WO2008018160A1

WO2008018160A1 - Method and apparatus for connecting printed wiring boards

Info

Publication number: WO2008018160A1
Application number: PCT/JP2007/000463
Authority: WO
Inventors: Naohito Nakaya; Ryuji Sekimoto
Original assignee: Nippon Avionics Co., Ltd.
Priority date: 2006-08-07
Filing date: 2007-04-26
Publication date: 2008-02-14
Also published as: KR100905404B1; JP4117851B2; TWI367699B; JPWO2008018160A1; CN101347052A; CN101347052B; KR20080049043A; TW200819002A

Abstract

Provided is a method for connecting printed wiring boards at least one of which is a flexible printed wiring board. A connecting terminal (4) of one printed wiring board (3) is placed over a connecting terminal (2) of the other printed wiring board (1) at a plurality of areas separated in a longitudinal direction by having an adhesive resin (6) in between. Pressure is applied to the both printed wiring boards while applying ultrasonic oscillation in a status where the adhesive resin is unhardened, and connecting terminals are bonded by solid phase intermetallic bonding at a plurality of areas. Since a time required for the solid phase intermetallic bonding (room temperature bonding) is extremely short, pressurization can be stopped without waiting for the resin to harden. Operating rate of the connecting apparatus is improved, and thus productivity is improved.

Description

Specification

Method and apparatus for connecting pudding and wiring board

Technical field

[0001] The present invention relates to a method for connecting a printed wiring board, at least one of which is a flexible printed wiring board, and a connection device directly used for carrying out this method.

Background art

[0002] In electronic devices, rigid printed wiring boards are used in places where component mounting is required, and flexible printed wiring boards are used in places where flexibility is required. Naturally, it is necessary to connect the rigid printed wiring board and the flexible printed wiring board, but in general, it is indirectly connected via a connector, or between solder-coated connection terminals by resistance welding. The method of soldering and connecting directly was adopted.

[0003] However, due to the recent progress of higher density and higher speed of electronic devices, the connection method using a connector is no longer used. On the other hand, the soldering method has been used by repeated efforts to increase the density. However, the solder protrusion has become a problem, and with the progress of finer pitches, short-circuiting to adjacent terminals has occurred. This problem has become frequent.

[0004] In order to solve this problem, a method using an anisotropic conductive film has been conventionally used for fine connections with a terminal-to-terminal pitch of approximately 300 m or less. In this method, the conductive particles are uniformly dispersed in the thermosetting resin film, and the conductive particles are sandwiched between the connection terminals of both printed wiring boards and thermocompression bonded. This is a method of maintaining a semi-permanent connection by simultaneously curing the thermosetting resin.

[0005] In this method, conduction is ensured by using elastic contact (mechanical contact by compressive stress of resin and restoring force of conductive particles) of conductive particles having a particle size of about 3 to 10 m. Therefore, the conductive path is narrowed, There was a problem that I could not. Another problem is that the resin film in which the conductive particles are uniformly dispersed is expensive and can only be applied to limited fields with high added value such as liquid crystal panels.

[0006] On the other hand, instead of using an anisotropic conductive film, an ultrasonic bonding method, which is one of the techniques for flip-chip mounting a semiconductor chip on a printed wiring board, is also used. In this method, a gold bump is formed on one of the connection terminals to be joined, and the gold bump is ultrasonically joined to achieve a connection by metal joining between the connection terminals of both printed wiring boards. However, since this ultrasonic bonding method requires the formation of gold bumps, there is a problem that the manufacturing process of the printed wiring board is complicated in terms of cost.

[0007] In order to solve this problem, a method has been proposed in which the conductors are brought into contact with each other in the resin using the plastic flow (Bingham flow) of a thermosetting resin. in this way

The mold is pressed against the connection terminal of the flexible printed wiring board to form periodic irregularities on the connection terminal, and the thermosetting resin that has been heat-cured is coated on it. The flexible printed wiring board that has been subjected to such processing is positioned on the second printed wiring board, and the connection is made by applying pressure while heating (see Non-Patent Document 1).

Non-Patent Document 1: Koichiro Kawate, “FPC Connection Technology Using Non-Conductive Film”, Proceedings of the 1st 3rd Microelectronics Symposium, 2000, 2003, 3 3 pages 2 to 3 3 5

[0008] In this method, when the overlapped connection terminal portion is pressurized and a stress exceeding the yield value is applied to the thermoset resin, the cured resin softens and exhibits fluidity (B i ngham pl ast ic). The plastic fluidized resin is discharged into the recesses on the surface of the connection terminals that have been processed to be uneven, and the connection terminals contact each other on the surface of the protrusions. Heating is performed in this state, and the connection terminal joint is raised to the recrystallization temperature or eutectic temperature to perform solid phase diffusion bonding, and at the same time, the resin is recured. Disclosure of the invention

Problems to be solved by the invention [0009] This method using plastic flow (Bingham flow) of the resin can secure a wider conductive path than the contact of conductive particles in the anisotropic conductive film so that the electrical performance is improved. However, this method has a problem that it is difficult to apply to a wide range of fields because it requires processing costs to form minute irregularities on the connection terminal portion of the printed wiring board.

[0010] Further, in this method, the terminal joint is heated and diffusion-bonded in a state where the stacked connection terminals are pressurized, and the resin is cured, so that the joining time is long, the processing efficiency is poor, and the operation of the apparatus is poor. There is a problem that the rate decreases. Furthermore, the resin to be used is selected so that the relationship between the pressure load and the viscosity is appropriate, and the recrystallization temperature of the terminal connection is considerably higher than the eutectic temperature (from 200 ° C to 2 ° C). It is necessary to use a special resin that cures at 35 ° C), and there is a small degree of freedom in resin selection; ε ϊ).

[001 1] The present invention has been made in view of such circumstances, and can increase the current that can flow compared to the case of using an anisotropic conductive film, and can use a special and expensive film or ultrasonic waves. It is an object of the present invention to provide a printed wiring board connection method that does not require the formation of gold bumps unlike the bonding method and can expand the field of use by reducing costs.

In addition, the present invention provides a printed wiring board connection method that has a greater degree of freedom in selecting a resin to be used than the method of Non-Patent Document 1 and can shorten the bonding time to increase the processing efficiency and increase the operating rate of the apparatus. The purpose is to provide.

Furthermore, an object of the present invention is to provide a printed wiring board connecting device used directly for carrying out this method.

Means for solving the problem

[0012] According to the present invention, this object is to connect a printed wiring board in which connection terminals of two printed wiring boards having at least one wiring board as a flexible printed wiring board are connected to each other in the longitudinal direction. This method is achieved by a printed wiring board connection method comprising the following steps a) to c).

a) The first printed wiring board and the connection terminals and the longitudinal direction of the first printed wiring board A second printed wiring board having connection terminals formed so as to overlap at a plurality of locations divided in a direction;

b) Overlay both connecting terminals at a plurality of locations with an adhesive resin between them; c) Apply pressure to both printed wiring boards while applying ultrasonic vibration while the adhesive resin is uncured. Are joined between solid-phase metals at multiple locations.

[0013] Further, the present invention provides a printed wiring board connecting apparatus for connecting the connecting terminals of two printed wiring boards in which at least one of the wiring boards is a flexible printed wiring board so as to overlap each other in the longitudinal direction: Adhere between the first connection terminal of the printed wiring board and the second connection terminal of the second printed wiring board on which the second connection terminal is formed so as to overlap with the first connection terminal at a plurality of locations separated in the longitudinal direction. Pressurizing means that pressurizes the joints of the two connection terminals stacked with the resin for sandwiching from above; excitation means for applying ultrasonic vibration to the joints of both connection terminals; A printed circuit board, characterized by comprising: a control means that is operated at times and applies ultrasonic vibration while applying pressure to both connection terminals while the adhesive resin is uncured. Providing equipment.

The invention's effect

[0014] According to the connection method 1 apparatus of the present invention, one connection terminal of the two printed wiring boards is overlapped with the other connection terminal at a plurality of locations separated in the longitudinal direction, so that the connection is made at a plurality of locations. It will be. Even if the connection (contact) area of each connection point is small, the total connection area is large, so that the current that can be passed can be increased. Moreover, it is not necessary to use a special and expensive film such as an anisotropic conductive film, or to process a gold bump like ultrasonic bonding, and the connection terminal used in the present invention is a circuit in the circuit pattern forming process of the wiring board. This can be dealt with by changing the pattern. For this reason, it is possible to reduce the cost and expand the application field.

[0015] The present invention uses so-called room-temperature solid-phase bonding, and the bonding resin sandwiched between the connection terminals is in an uncured state only for the time during which solid-state metal bonding (room temperature bonding) is performed by pressing the overlapping connection terminals. I just need it. There is no need to use special and expensive resin. The degree of freedom in selecting fat increases. Here, the time required for solid-phase metal bonding (room temperature bonding) is extremely short, and it is possible to release the pressure without waiting for the resin to solidify. Therefore, it is necessary to remove two bonded wiring boards from the connection device. The resin can be cured. For this reason, the operating rate of the connection device is increased and productivity can be increased.

Brief Description of Drawings

FIG. 1A is a plan view showing an outline of connection terminals used in a printed wiring board connection method and apparatus according to Embodiments 1 and 2 of the present invention.

[Fig. 1B] Sectional view taken along line 1B_1B in Fig. 1A

FIG. 2 is a schematic process diagram showing the first half (a) to (d) of the connection process of the printed wiring board of the present invention.

FIG. 3 is a schematic process diagram showing the latter half (e) to (g) of the connection process of the printed wiring board of the present invention.

[Fig.4] Diagram showing the connecting terminal part (shaded area) to be joined in the connection process

[Figure 5] Diagram showing the experimental results of the relationship between contact pressure and contact resistance between electrolytic copper plated wiring patterns

FIG. 6 is a conceptual diagram showing an embodiment of a printed wiring board connecting device according to the present invention.

FIG. 7 is a conceptual diagram showing another embodiment of the printed wiring board connecting device according to the present invention, and shows a device combining the temporary crimping device and the final crimping device.

FIG. 8 is a diagram showing an embodiment of an arcuate ladder type connection terminal.

FIG. 9 is a diagram showing an example of a saw blade-type ladder connection terminal.

FIG. 10 is a diagram showing an example of a connection terminal provided with a blanking pattern to form a ladder type.

[Fig. 11] Diagram showing an embodiment in which both connection terminals are cantilevered ladder type terminals.

FIG. 12 is a diagram showing an embodiment of a connection terminal having a substantially semicircular arc shaped child terminal.

[Fig.13] Waveform (Zigzag type) Diagram showing an example of connection terminal

FIG. 14 is a diagram showing an example of a discontinuous land type connection terminal, in which the upper part is a plan view and the lower part is a cross-sectional view.

FIG. 15 is a view showing another embodiment of the discontinuous land type connection terminal, and the upper part is a plan view. The lower part is a cross-sectional view.

FIG. 16 is a view showing another embodiment of the discontinuous land type connection terminal, wherein the upper part is a plan view and the lower part is a cross-sectional view.

FIG. 17 is a view showing an embodiment of an etching step type connection terminal, wherein the upper part is a plan view and the lower part is a cross-sectional view.

Explanation of symbols

1 Flexible printed wiring board (first printed wiring board)

2 First connection terminal

3 Rigid printed wiring board (second printed wiring board)

Second connection terminal with 4 child terminals

4 a child !!

4 an nickel plating layer

4 a k gold-plated layer

4 b Long terminal

5 mounting table

6 Thermoplastic resin film (adhesive resin)

7 Ultrasonic head

8 Teflon sheet

9 Joint

2 0, 2 0 B Positioning table

2 2, 2 2 B mounting table

2 4 Position controller

2 6 Supply means

2 8 Retaining plate

3 4, 3 4 A, 3 4 B Pressurizing means

3 6 Pressure unit

3 8 Excitation means

4 0, 4 0 B ultrasonic horn 4 2 Ultrasonic transducer

4 3, 4 3 A 4 3 B Heating means

4 4 Frame material

5 0 Pressure head

5 2 Control unit

6 0 6 0 A '6 0 J ¾ 1 u meta

6 2 6 2 A '6 2 J Terminal 2

6 4, 6 4 A '6 4 C Rigid blind wiring board

7 0 7 0 A '7 0 B Flexible printed wiring board

BEST MODE FOR CARRYING OUT THE INVENTION

[0018] It is a necessary condition that at least one printed wiring board is a flexible printed wiring board, but the other printed wiring board is not limited to this. It is desirable that the wiring pattern of either printed wiring board has a thickness (generally 5 m or more) that allows the adhesive resin to be discharged when pressure is applied, and that local stress can be concentrated on the connection terminals. . Of course, the substrate material of the wiring board may be an organic printed wiring board, but other wiring boards, such as inorganic printed wiring boards such as ceramics or glass, may also be used.

[0019] The connection terminal of one of the wiring boards used here may be a ladder-type terminal including a plurality of child terminals that are separated and provided at intervals in the longitudinal direction of the connection terminal. In this case, align the multiple child terminals so that they overlap with the connection terminals of the other wiring board.

[0020] Here, the child terminal can be formed in a comb-teeth shape that protrudes perpendicularly from the longitudinal longitudinal portion in the longitudinal direction to one side. In this case, the other connecting terminal can be formed in a straight line having a narrow width so that the child terminals overlap in the longitudinal direction. In addition, the other connection terminal can be positioned symmetrically with respect to the straight line in the longitudinal direction so that the child terminals of both connection terminals overlap each other.

[0021] The slave terminal may have a shape (ladder type) in which two parallel longitudinal longitudinal portions extending in the longitudinal direction are connected at predetermined intervals. In this case, each small terminal The shape of the concave portion formed between the two may be a quadrangle, an ellipse (ellipse), a diamond shape, or the like, and the other connection terminal may be aligned so that the concave portion is longitudinally cut in the longitudinal direction.

[0022] —The connection terminal is formed in a waveform (zigzag shape), and the other connection terminal is formed in a straight line or a waveform with the same period (zigzag shape) so that both connection terminals overlap each other in the longitudinal direction at predetermined intervals It can also be combined.

[0023] The negative connection terminal may be a discontinuous land type in which lands such as via holes connected to the circuit pattern of the wiring board are arranged on the surface of the wiring board at a predetermined interval. For example, via holes connected to the inner layer circuit pattern of the wiring board are used as connection terminals, and the connection terminals of the other wiring board are superimposed on the lands of these via holes.

[0024] The first connection terminal may be a step type formed such that a large number of recesses and projections crossing in the width direction are alternately arranged in the longitudinal direction. This step can be formed by an etching process used in the circuit pattern formation process.

[0025] In the printed wiring board connection method of the present invention, both the printed wiring boards are pressurized while applying ultrasonic vibration while the adhesive resin is uncured, and the connection terminals are joined between the solid-phase metals at a plurality of locations. (Process c)). Curing of the adhesive resin may be performed simultaneously with solid-phase metal-to-metal bonding by heating and pressing in step c). However, the adhesive resin may be cured in a step separate from step c). In that case, the pressure of the adhesive resin can be released, and both printed wiring boards can be moved from the connection device for solid-phase metal-metal bonding, and the adhesive resin can be cured by another device. As a result, it is possible to shorten the use time of the connecting device for performing solid-phase metal-to-metal bonding and to increase the operating rate of the device.

[0026] In addition, in the step b) in which both connection terminals are stacked at a plurality of positions with an adhesive resin interposed therebetween, both connection terminals of both printed wiring boards may be pressurized and temporarily pressed. In this case, in step c), the pressure-bonded both printed wiring boards are pressed while applying ultrasonic vibration, and the main crimping is performed to join the connecting terminals between the solid-phase metals at a plurality of locations.

[0027] Even if the adhesive resin used in step b) is a thermoplastic resin, it is a thermosetting resin. There may be. In the case of a thermoplastic resin, when the connecting terminal joint is vibrated and pressurized, the resin is softened and heated to make it flowable (uncured). This heating also has the effect of promoting solid-phase metal-to-metal bonding (process C)). After indirect solid-phase metal bonding (step C)), the thermoplastic resin can be cured by releasing the pressure on the thermoplastic resin and then lowering the temperature. It is desirable that the pressure applied to the thermoplastic resin is released when the thermoplastic resin exhibits a strength of approximately 50% of its maximum adhesive strength.

[0028] When a thermosetting resin is used as the adhesive resin, an uncured and tacky resin is used. However, since solid-metal-to-metal bonding (step c)) can be promoted by raising the temperature, in this step c), the thermosetting resin is not cured and is heated to a temperature at which its adhesiveness can be maintained. Is desirable. It is preferable to heat to a temperature lower than the melting temperature of the connection terminal and the adhesive resin does not cure. In this case, it is desirable to release the pressure applied to the thermosetting resin after solid-phase metal-to-metal bonding (step c)), and then raise the temperature to cure the thermosetting resin.

[0029] Regardless of whether a thermoplastic resin or a thermosetting resin is used as the adhesive resin, both connection terminals of both printed circuit boards are used in step b) in which both connection terminals are stacked at a plurality of positions with the adhesive resin interposed therebetween. Can be pressure-bonded and temporarily bonded, followed by solid-phase metal-to-metal bonding (step c)). In the case of a thermoplastic resin, in step b), heating is performed so that the thermoplastic resin is softened, and both printed wiring boards are temporarily bonded.

[0030] In the case of a thermosetting resin, in step b), heating is performed until the adhesiveness is maintained, and both printed wiring boards are temporarily crimped, and in step c), the thermosetting resin is uncured. Press-bond both printed wiring boards while applying ultrasonic vibration, and perform final crimping to join the connection terminals between the solid-phase metals at multiple locations. The temperature is then raised to cure the thermosetting resin. At this time, after the main pressure bonding by solid-phase metal-to-metal bonding (step c)), the pressure on the thermosetting resin may be released, and then the temperature may be raised to cure the thermosetting resin. In this case, the thermosetting resin is approximately 50% of its maximum cure. If the pressure applied to the thermosetting resin is released at the time when the hardness is exhibited, the wiring board can be moved from the connecting device while ensuring the mechanical strength of the joint in a short time. Moreover, if the adhesive exhibits a hardness of 50% when the wiring board is moved, it is possible to prevent a decrease in reliability. The wiring board moved from the connecting device can be put in a heating furnace to completely cure the thermosetting resin.

[0031] The adhesive resin may be a photo-curing type (ultraviolet-curing type), and in this case, the resin is cured by light irradiation after solid-phase metal-to-metal bonding (step c).

[0032] Ultrasonic vibration applied at the time of pressurization breaks down the oxide film at the joint interface by plastic deformation, and causes the clean metal surfaces (new surfaces) of both connection terminals to directly adhere to each other at the atomic level. Phase normal temperature bonding). That is, this joining method joins the joined portion in a solid phase without melting the joined portion. It is known that the solid-phase bonding method includes the normal temperature bonding that pressurizes and bonds at room temperature, which is the method of the present invention, and the diffusion bonding that pressurizes at a high temperature (recrystallization temperature, eutectic temperature or higher). As described above.

[0033] Diffusion bonding is maintained at a high temperature for a long time, and bonding is performed by diffusion between atoms. In other words, the bonded interface is formed by the cleave phenomenon caused by pressurization, the voids are reduced by the sintering phenomenon, and the crystal grain boundary formed at the bonded interface moves to complete the bonding. The method disclosed in Non-Patent Document 1 corresponds to this diffusion bonding.

[0034] In the present invention, room temperature bonding is used, and the oxide film is broken by the unevenness of the atomic level order of the bonding surface by pressurization. However, by applying ultrasonic vibration, the destruction of the oxide film is promoted. It promotes solid-phase bonding by promoting adhesion between metals at the atomic level. Ultrasonic vibration may be constantly applied during pressurization. Force pressurization may be changed in two stages, temporary press-bonding and final press-bonding, and ultrasonic waves may be applied only during the main press-bonding.

[0035] It is desirable to apply ultrasonic vibration mainly in a direction perpendicular to the joint surface. However, ultrasonic vibration may be applied in the horizontal direction parallel to the joint surface. Even ultrasonic vibration applied in the horizontal direction includes both vertical and horizontal components with respect to the joint surface. Therefore, vertical vibration is also applied to the joint surface. In the case of such ultrasonic vibration applied in the horizontal direction, a film with a low coefficient of friction such as Teflon (registered trademark) is interposed between the excitation part and the joint part (wiring board). The vibration of the horizontal component can be weakened to make the vertical component the main component. The bonding surface of both connection terminals may be irradiated with an Ar ion beam to be cleaned and activated, and immediately contacted and pressurized.

[0036] The printed wiring board connection device of the present invention comprises a pressurizing means, a vibration means, and a control means, and a first connection terminal of the first printed wiring board and a second connection of the second printed wiring board. The joint of the two connection terminals, which are stacked with the adhesive resin between them, is pressed from above by the pressing means. At the same time, the vibration means applies ultrasonic vibration to the joint of both connection terminals. The control means operates the pressurizing means and the vibration means at the same time, and applies ultrasonic vibration while applying pressure to both connection terminals in an uncured state of the adhesive resin, thereby joining the solid phase metal.

[0037] After the solid-phase intermetallic bonding is completed, it is necessary to cure the uncured adhesive resin. Therefore

A heating means may be provided that heats and cures the uncured adhesive resin after the connection terminals are joined between the solid phase metals. Alternatively, the control means may control the pressure means so that the pressure is released when the adhesive resin is in an uncured state. In this case, the joined wiring board removed from the connection device is heated by another device to harden the resin.

[0038] The printed wiring board connecting device is provided with positioning means, the first printed wiring board and the second printed wiring board are sandwiched between the connecting terminals, and the second connecting terminal is the first connecting terminal. It is desirable to hold one connection terminal so that it overlaps at multiple locations separated in the longitudinal direction.

The positioning means includes a positioning table that supports the second printed wiring board from below and can be positioned on a horizontal plane, and supplies the first printed wiring board above the second printed wiring board. It can be formed with a supply means for holding the connection terminals in the longitudinal direction. Here the positioning table is water It is recommended to use a table that can determine the position of the X_Y direction orthogonal to the plane and the rotation direction around the vertical axis (0 direction).

[0039] A holding plate may be provided in the supply means. For example, the upper second printed wiring board may be sucked and adsorbed on the lower surface of the holding plate by suction negative pressure, and transferred and supplied. Alternatively, it may simply be a supply means for gripping and transferring and supplying the wiring board.

[0040] The pressurizing means includes, for example, a pressurizing unit that pressurizes the upper wiring board downward and a vibration unit that mainly applies ultrasonic vibration in the vertical direction to the wiring board. In this case, the excitation unit can be formed by an ultrasonic horn and an ultrasonic transducer fixed to the ultrasonic horn, and the pressurization unit can pressurize the wiring board via the ultrasonic horn.

[0041] The excitation means is formed of an ultrasonic horn and an ultrasonic vibrator attached to the ultrasonic horn, and the pressurizing means can be configured to apply pressure to both printed wiring boards via the ultrasonic horn. It is. You may provide a heating means in this ultrasonic horn. In this case, the control means controls the heating means to heat the connecting terminal joints to a temperature that enables solid-phase metal joining under the uncured state of the adhesive resin.

[0042] Both the printed wiring boards in which the joint portions of both connection terminals are positioned and overlapped by the positioning means are subjected to ultrasonic vibration and pressure on the positioning means by the excitation means and the pressurizing means means. Both connection terminals may be joined together. After positioning, both connecting terminals can be crimped and joined in one pressurization process.

[0043] Alternatively, the crimping after positioning can be performed in two stages, a temporary crimping and a final crimping. In this case, the vibration means is provided with a heating means for heating the adhesive resin, and the control unit controls the positioning means so that the second connection terminal overlaps the first connection terminal at a plurality of locations separated in the longitudinal direction. After the positioning, the pressing means and the heating means are controlled to apply pressure while heating the adhesive resin so as to develop or maintain the tackiness, so that both printed wiring boards are not easily detached. Crimp. After that, the control means controls the heating means, the pressurizing means, and the vibration means, and applies both pressure and ultrasonic vibration sufficient for solid-phase metal bonding to both pre-bonded printed wiring boards. Perform terminal crimping.

[0044] Temporary pressure bonding and main pressure bonding can also be performed by separate apparatuses. in this case, The temporary crimping apparatus performs temporary crimping by heating and pressurizing the positioning means and the connection terminals of both printed wiring boards positioned by the positioning means to such an extent that the adhesive resin can exhibit or maintain adhesiveness. Heating and pressurizing means are provided. On the other hand, this crimping device is provided with vibration means and pressure means, and both connection terminals are applied by applying ultrasonic vibration and pressure to both printed wiring boards that have been positioned and provisionally crimped from the temporary crimping device. Join. With such a configuration, the operation time of the crimping device that applies ultrasonic vibration can be shortened, and as a result, the operating rate can be increased.

[0045] The reason why ultrasonic waves are applied in the present invention is to promote plastic deformation of the unevenness on the surface contact of the electrode (joining terminal) by compressive stress. For this purpose, longitudinal vibration is preferably applied. . Previously, it was thought that plastic deformation was possible even when lateral vibration was applied. However, on the actual joint surface, even if it is a transverse vibration, the stress has a vector component in the vertical direction, so that the plastic deformation of the unevenness was promoted and the joint could be joined. This means that a slippery material such as a Teflon (trademark) sheet can be inserted between the ultrasonic head and the printed wiring board as a release material, or ultrasonic vibration and pressure can be applied without fixing the wiring board. This is an experimental fact that is indirectly suggested by the fact that good jointability can be obtained even when the relative movement in the horizontal direction is possible.

Principle

Next, the bonding principle and bonding conditions of the present invention will be described. As described above, the conventional anisotropic conductive film needs to use fine conductive particles. In Non-Patent Document 1, material costs and processing costs increase due to the formation of minute irregularities. In order to avoid these problems, the present invention contemplates a method of directly ultrasonically bonding the connection terminals of a printed wiring board under a solid phase. However, when connecting the printed circuit boards, the connection terminals are stretched in the same direction and patterned, so that the contact area where these connection terminals are stacked is wide for simple ultrasonic bonding. Too much. The following problems occur when the contact area between the connection terminals is large.

[0047] First, if the contact area is large, the non-contact portion of the terminal that should be discharged from the resin is reduced. The resin sandwiched between the terminals is less likely to be discharged. For this reason, the contact between the connection terminals becomes insufficient. The second problem is that of springback. In order to cause the adhesion phenomenon due to solid-phase metal bonding, the load necessary to cause plastic deformation must be applied to the connection terminal, but this load must be increased according to the contact area. So inevitably grows. At the same time, this load causes elastic deformation of the printed wiring board itself, and if this load is removed after the joining process is completed, springback will occur. For this reason, the joint interface once joined in the joining process is also peeled off. In this way, a good connection terminal cannot be joined simply by using a method called ultrasonic bonding.

[0048] However, since there is an advantage that material costs and processing costs can be reduced, a method of directly ultrasonically connecting the connection terminals of a printed wiring board under a solid phase is considered useful. Therefore, we decided to search for a solution to the above problem.

As described above, in order to directly ultrasonically connect the connection terminals of the printed wiring boards under the solid phase, it is necessary to carry out without applying an excessive load. In other words, since the load increases in proportion to the contact area between the connection terminals, the inventors of the present application secure the necessary load (pressure) while reducing the contact area and sufficiently reduce the contact resistance of the joint. We decided to consider a solution from the aspect of the structure of the connecting terminals that can be made.

[0049] In view of this, first, it was decided to investigate the required minimum load. First, the semiconductor chip was subjected to ultrasonic bonding in a state where a resin serving as an adhesive layer was previously supplied to the bonding interface. Let's take a look at flip-chip mounting on a reprint printed circuit board. When the gold bumps formed on the semiconductor chip are macroscopically plastically deformed, the resin is discharged from the bonding surface, the gold bumps and the printed circuit board on the printed circuit board are in direct contact with each other, and ultrasonic bonding enables metal-to-metal bonding. It is possible. In this case, no molten structure is observed in the joint, so it is considered that the solid phase bonding is close to mutual diffusion. For this purpose, it has already been found that a pressure of about 15 OMPa (a macroscopic average load per bump deformation area) is required at least at the connection interface. This is the case of gold bumps formed on a semiconductor chip. On the other hand, in the case of the printed wiring board targeted by the present invention, a general wiring material is plated with electrolytic copper. Since the yield value of the copper-plated wiring pattern is several times that of gold, in order to plastically deform this copper-plated wiring pattern macroscopically, 15 times the OMPa in the case of gold bumps It was expected that pressure would be required.

Therefore, we decided to experimentally confirm the relationship between the contact surface pressure and the contact resistance required to bond copper-plated wiring patterns by the ultrasonic bonding method. Figure 5 shows the experimental results. This wiring pattern is a copper plating with nickel plating and gold plating. From the results of this experiment, when the contact surface pressure is approximately 1500 MPa or more, the contact resistance is approximately 1.75 ohms and there is almost no change. By applying a pressure of approximately 15 OMPa, sufficient conductivity is ensured. I knew what I could do. In other words, the pressure is the same as that for gold bumps.

[0051] Here, as a result of considering that a sufficiently low contact resistance can be secured with a pressure equivalent to that of a gold bump of approximately 15 OMPa, which is contrary to expectations as described above, the following has been found.

Analyzing the bonding interface using a method such as cross-sectional analysis, the surface of the copper plating pattern (nickel plating and gold plating on the surface) is equivalent to the surface roughness / m. There were minute irregularities in the unit. At a pressure of 1 5 0 M Pa, the copper plated wiring pattern does not undergo plastic deformation macroscopically. However, even at this pressure, the tip of the minute unevenness in m units and the metal plating applied to the surface were plastically deformed, and sufficient pressure was applied to the resin discharge in this minute portion. In addition, when there was no nickel or gold plating, there was a minute unevenness on the copper plating surface, which was plastically deformed.

[0052] That is, in ultrasonic bonding between electrolytic copper plated wiring patterns, the tips of minute bumps and bumps formed on the surface of jum units formed on the surface are plastically deformed by the load and ultrasonic vibration, and at the same time the resin is discharged. It was done that the contacted metal surface caused an adhesion phenomenon to form an intermetallic bond. Thus, a pressure of about 1 5 0 MPa In the joining method in which ultrasonic vibration is applied over the surface, the surface roughness of the connection terminal electrode of the printed wiring board is an important parameter. In this regard, the printed circuit board pattern manufactured using the normal manufacturing process has a 10-point average roughness of approximately 0.5 m. If this level of unevenness is present, copper This is considered to be sufficient for ultrasonic bonding between metal patterns. In other words, it was found that no special process was required to generate irregularities on the surface of the wiring pattern.

[0053] Next, the effect of the pressure of 15 OMPa on the substrate of the printed wiring board will be examined.

Calculate the case where the connection terminals that run parallel to each other in the same direction are crimped in the same direction.

As an example, consider a connection part consisting of 30 terminals with a width of 0.1 mm and a length of 1.5 mm.

When these connection parts are overlapped, the connection area is 0.15 mm ² per connection terminal, so the total of 30 connection terminals is 4.5 mm ² . At a pressure of 1 50 MPa, a load of 150 N per 1 mm ² is applied, so a total load of 30 N will apply a load of 675 N. Since this load is applied to the entire connection terminal, it is also applied to the substrate of the underlying printed wiring board, which causes significant elastic deformation of the substrate of the printed wiring board. Therefore, when the load is removed, the corresponding elastic restoring force works and the joint is destroyed. Of course, if a material having a high elastic modulus is used for the substrate of the printed wiring board, it is possible to avoid breakage of the joint. However, even in this case, the problem remains that the mounting apparatus becomes large in order to apply a high load.

[0054] Further, in the conventional solid phase diffusion bonding shown in Non-Patent Document 1, it is necessary to heat the bonding interface to a temperature equal to or higher than the eutectic temperature or the recrystallization temperature, and to maintain the pressure at this temperature for a certain period of time. is there. This increases the processing time. Therefore, room temperature bonding (room temperature micro bonding) is used in the present invention. In other words, the bonding surfaces should be thoroughly cleaned and bonded with slight pressure, and then the resin is cured to reinforce the bonded portion. It is.

[0055] As a result of the investigation described above, as a result of reducing the contact area of each divided joint portion of the connection terminal, the structure of the connection terminal and such a structure that does not easily cause such breakdown of the joint are obtained. The inventors have invented a method and apparatus for connecting printed wiring boards using printed wiring boards having connecting terminals.

Example 1

FIG. 1A is a plan view showing a printed wiring board according to an embodiment of the present invention, and a large number of child terminals project at right angles on one side of the connection terminal. FIG. 1B is a cross-sectional view taken along line 1B-1B of FIG. 2 and 3 are schematic process diagrams showing a connection process between the lower rigid printed wiring board and the upper flexible printed wiring board having the connection terminals of FIG. FIG. 4 is a plan view showing a portion (shaded portion) to be joined in the connection process of FIGS.

[0057] In FIGS. 1A and 1B, 3 is a printed wiring board, 4 is a connection terminal formed on the printed wiring board 3, and the longitudinally long portion 4b in the longitudinal direction is located on one side from one side. A plurality of child terminals 4a are provided. In the present invention, this child terminal 4a is used for connection between printed wiring boards. 4 an is the nickel plating layer formed by electrolysis or electroless treatment on the surface of the connection terminal 4 and the child terminal 4 a, 4 ak is the same treatment method formed on the surface of the nickel plating layer 4 an It is a gold-plated layer.

In FIG. 2, 1 is a flexible printed wiring board (first wiring board) serving as an upper wiring board, on which a connection terminal 2 is formed. 3 is a rigid printed wiring board (second wiring board) to be a lower wiring board, on which a connection terminal 4 is formed, and the connection terminal 4 is provided with a child terminal 4a of FIG. 1A. Yes. 5 is a mounting table for the rigid printed wiring board 3 when the flexible printed wiring board 1 and the rigid printed wiring board 3 are connected, and 6 is a thermoplastic resin film serving as an adhesive layer.

In FIG. 3, reference numeral 7 denotes an ultrasonic head as the vibration means and pressure means of the present invention, which also has a heating means. This ultrasonic head 7 is a flexi Connect the connecting terminals 2 and 4 by applying ultrasonic vibration while heating and heating the Bull Printed Wiring Board 1 and the Rigid Blind Wiring Board 3 with the connecting terminals 2 and 4 superimposed on each other. Reference numeral 8 denotes a Teflon sheet that is used as a release material for easily releasing the head 7 when the thermoplastic resin 6 protrudes from between the connection terminals and contacts the ultrasonic head 7 during pressurization. This Teflon sheet 8 functions to reduce the vibration component of the ultrasonic vibration in the horizontal direction of the wiring board, and mainly to apply the vibration component in the vertical direction of the wiring board to the joint 9 of both the connection terminals 2 and 4.

Fig. 4 shows the joint 9 between the connecting terminals 2 and 4 in a diagonal line when the flexible printed wiring board 1 and the rigid blind wiring board 3 are connected.

[0060] (Formation of child terminal)

First, the method for forming the child terminal 4a shown in FIGS. 1A and 1B will be described. In addition, since this formation method uses a well-known method as it is, illustration is abbreviate | omitted.

First, a printed wiring board on which copper foil is laminated is prepared. Then, for example, a photosensitive resist is applied to the surface of the copper foil, exposed to ultraviolet rays using a photomask, and further developed to form an etching resist having a predetermined wiring pattern on the surface of the copper foil. Next, unnecessary portions of the copper foil not covered with the etching resist are dissolved by etching using, for example, an aqueous solution of ferric chloride to form connection terminals 4 and child terminals 4a having a predetermined wiring pattern.

[0061] Thereafter, the etching resist is removed in an alkaline solution. After that, apply plating resist to the parts excluding connection terminal 4 and child terminal 4a, and then apply nickel plating and gold plating in this order, and then remove the adhesive resist. In this way, the connection terminal 4 and the child terminal 4a in which the nickel plating layer 4 an and the gold plating layer 4 ak are formed are formed.

[0062] Since these nickel plating layer 4 an and gold plating layer 4 ak are exclusively considered for ultrasonic bonding, not only this but also other metal platings that can be bonded to each other such as tin or tin alloy But you can. Also, cleaning the ultrasonic bonding surface is also effective for ultrasonic bonding, so instead of plating, plasma processing, etc. A surface cleaning process may be performed on the connection terminals.

[0063] An example of the size and number of the child terminals is that the inter-metal bonding by the child terminals 4a is not broken by the elastic restoring force, and the area of the child terminals 4a and the load at the time of connection are shown. The relationship will be described. It has already been found that a nearly constant contact resistance can be obtained by applying a pressure of 15 OM Pa as described above. It has also been found that when the load applied to the connection terminal 4 and the printed wiring board 3 is about 10 ON, the joint due to elastic restoring force is not broken.

[0064] For example, the width of the vertically long portion (main terminal) 4 of the connection terminal 4 is 0.1 mm, and the connection terminals 4 are arranged at a pitch of 0.3 mm. The width of the child terminal 4 a (the length in the longitudinal direction of the connection terminal 4) is 0.05 mm, and the length (the length in the direction perpendicular to the longitudinal direction of the connection terminal 4) is 0.15 mm. Five child terminals 4a are formed in the length direction of the connection terminal 4 at intervals of 5 mm (Fig. 1A).

[0065] The load at this time is calculated as follows. Connecting superimposed rigid Brin preparative child terminal 4 a and connection terminals 2 of the flexible printed wiring board 1 of the wiring board 3, the area of the portion to be joined becomes 0. 005mm ^2. Contact area per connection terminal since provided five child terminals Ri per 1 connection terminal becomes 0. 025 mm ^2. Therefore, if 30 connection terminals are used as in the conventional example, the contact area will be 0.75 mm ^{2 in} total, and when a pressure of 1 50 MPa is applied, a load of 1 1 2 N will be applied to the connection terminals 4 and the printed wiring board. 3 is applied to the base material. Therefore, if such a child terminal 4a is used for connection, the joint breakage due to the elastic restoring force does not occur.

[0066] (Connection between printed wiring boards)

Next, a method for connecting the flexible printed wiring board 1 and the rigid printed wiring board 3 will be specifically described.

First, a rigid printed wiring board on which the flexible printed wiring board 1 on which the connection terminals 2 are formed and the connection terminals 4 on which the child terminals 4a are projected is prepared (FIGS. 2 (a) and (b)).

[0067] Next, the surface on which the rigid printed wiring board 3 is formed with the connection terminals 4 (component mounting surface) Place it on the mounting table 5 with the) facing up (Fig. 2 (c)). Next, connect the flexible printed wiring board 1 with the connection terminal 2 on the bottom, and sandwich the thermoplastic resin film 6 between the flexible printed wiring board 1 and the rigid printed wiring board. Position and overlap the sub terminals 4a of the wiring board 3 (Fig. 2 (d), Fig. 4).

This alignment is performed by the following known method, for example.

If the transparency of the flexible printed wiring board 1 and the thermoplastic resin film 6 is sufficient, the alignment is made with reference to the alignment mark on the rigid printed wiring board 3 through the flexible printed wiring board 1 and the thermoplastic resin film 6. Perform the adjustment. On the other hand, if either the flexible printed wiring board 1 or the thermoplastic resin film 6 is opaque, the connecting terminal 2 of the flexible printed wiring board 1 and the connecting terminal 4 of the rigid printed wiring board 3 and the child terminal 4 a in advance. The image is aligned and aligned using an automatic recognition mechanism that uses image recognition.

[0069] Next, the ultrasonic head 7 is placed on the portion corresponding to the position of each of the connection terminals 2 and 4 a from the back side of the flexible printed wiring board 1 (upper side of Fig. 3 (e)). Apply pressure (Fig. 3 (e)). At this time, the ultrasonic head 7 is set in advance to a temperature corresponding to the softening temperature of the thermoplastic resin film 6. In this way, the ultrasonic head 7 applies a predetermined temperature and a predetermined pressure to the flexible printed wiring board 1 and the flexible printed wiring board 3. As a result, the thermoplastic resin film 6 is softened and the connection terminal 2 of the flexible printed wiring board 1 and the connection terminal 4a of the rigid printed wiring board come into contact with each other. In this state, ultrasonic vibration (direction is the front and back direction in the figure) is applied from the ultrasonic head (Fig. 3 (f)). The ultrasonic vibration direction is horizontal to the substrate, but because the Teflon sheet 18 is used as a release material, the horizontal vibration component is weakened against the substrate, and the vertical vibration component is applied to the substrate joint. Applied, solid phase metal bonding is possible. Of course, the ultrasonic vibration direction may be perpendicular to the substrate (up and down in the figure) from the beginning.

[0070] The application time of the ultrasonic vibration is approximately 0.5 seconds as a guide. This time The metal-to-metal joint having the necessary holding force is completed. After this time has elapsed, the ultrasonic head 7 is pulled away from the top of the flexible printed wiring board 1. Then, the connection portion that was generating heat by the ultrasonic head 7 is gradually cooled by heat dissipation, and the thermoplastic resin film 6 is solidified accordingly, and a stable joining is completed (FIG. 3 (g)). At this time, both the wiring boards 1 and 3 may be unloaded from the mounting table 5 without waiting for the resin film 6 to harden. Connection terminals 2 and 4 are already fixed by solid-phase metal bonding.

Example 2

[0071] Instead of the thermoplastic resin film 6 of Example 1, a thermosetting resin may be used for the adhesive layer. The only difference is whether it hardens when heated or hardens when cooled after heating, and has the same effect as an adhesive layer. The connection method between the printed wiring boards when using the thermosetting resin is basically the same as the connection method between the flexible printed wiring board 1 and the rigid printed wiring board 3 described in the first embodiment. Therefore, the differences will be explained mainly using Figures 2 and 3 as necessary.

[0072] When the thermosetting resin is a liquid resin, the thermosetting resin is supplied by printing or a dispensing method. On the other hand, when using a semi-cured resin film, it is temporarily crimped to the rigid printed wiring board 3 or the like, or sandwiched and placed as described above.

[0073] In this way, the flexible printed wiring board is sandwiched between the thermosetting resins.

Position 1 and the rigid blind circuit board 3 with their joints aligned. Then, the ultrasonic head 7 is set to the curing temperature of the thermosetting resin, and as described above, a predetermined temperature and a predetermined temperature are applied to the flexible printed wiring board 1 and the rigid printed wiring board 3 with the ultrasonic head 7. Apply pressure. By doing so, the connection terminal 2 of the flexible printed wiring board 1 and the connection terminal 4 a of the rigid printed wiring board 3 come into contact before the thermosetting resin is cured. In this state, ultrasonic vibration (direction is in the direction of the front and back of the figure) is applied from the ultrasonic head (Figure 3 (f)).

[0074] The application time of ultrasonic vibration is approximately 0.5 seconds as a guide. This time Thus, solid-phase metal-to-metal bonding having a necessary holding force is completed. After the elapse of this time, the temperature and pressure are applied by the ultrasonic head 7 for a predetermined time until the thermosetting resin is cured. Thereafter, the ultrasonic head 7 is pulled away from the top of the flexible printed wiring board 1. In this way, the thermosetting resin solidifies and completes a stable bond (Fig. 3 (g)).

[0075] The curing of the thermosetting resin described above is performed in place of heating and pressing with the ultrasonic head 7.

The resin can be taken out in an uncured state and placed in a heating furnace. In this case, it is preferable to cure by heating and pressing from the ultrasonic head 7 so that the thermosetting resin has a curing degree of about 50% of the complete curing degree. Then, the ultrasonic head 7 is pulled away from the flexible printed circuit board 1. Then, the flexible printed wiring board 1 and the rigid printed wiring board 3 to which the adhesive layer made of a thermosetting resin is connected in a semi-cured state are separately placed in a heating furnace, and the heating furnace is completely covered with the thermosetting resin. Set the temperature to harden, hold for a full cure time, and then remove. In this way, the thermosetting resin solidifies and completes a stable bond (Fig. 3 (g)).

[0076] The curing temperature and curing time of the thermosetting resin can be set in consideration of the curing characteristics of the thermosetting resin used. This curing characteristic can be grasped in advance by a method for predicting the curing rate of a thermosetting resin previously filed by the applicant of the present application (Japanese Patent Application No. 2 0 06-1 4 7 1 0 4).

Example 3

FIG. 6 is a conceptual diagram showing an embodiment of a terminal connection device for a printed wiring board according to the present invention. In this figure, 20 is a positioning table, which can be positioned on the horizontal plane in the orthogonal direction (X_Y direction) and the rotation angle around the vertical direction (0 direction). A mounting table 22 is fixed on the upper surface of the table 20, and a rigid printed wiring board (second wiring board) 3, which is the other wiring board, is fixed thereon. The second connection terminal 4 of the second wiring board 3 is the ladder type of the first embodiment, and the resin film 6 is pasted thereon. The position of the table 20 is controlled by the position controller 24. [0078] 26 is a supply means, and the flexible printed wiring board (first wiring board) 1 which is the other wiring board is supplied above the rigid printed wiring board (second wiring board) 3, and both wirings Hold the connection terminals 2 and 4 of the plates 1 and 3 in the longitudinal direction. The supply means 26 is moved forward and backward by the position controller 24 and positioned. This supply means 26 has a holding plate 28 on its lower surface. The holding plate 28 holds the flexible printed wiring board 1 by sucking the lower surface by, for example, negative intake pressure. The supply means 26 and the positioning table 20 constitute a positioning means in the present invention. Reference numeral 30 denotes a suction control unit that controls the suction force of the holding plate 28.

[0079] 3 4 is a pressurizing means, and a pressure part 3 6 that pressurizes the overlapping part of the connection terminals 2 and 4 of both wiring boards 1 and 3 downward from the upper side of the flexible printed wiring board 1; And a vibrating means 38 for applying ultrasonic vibration mainly in the vertical direction (vertical direction of the wiring board) from the upper side of the flexible printed wiring board 1. The vibration means 38 includes an ultrasonic horn 40 made of a vertically long metal member, and an ultrasonic vibrator 42 fixed to the upper end of the ultrasonic horn 40. The ultrasonic horn 40 resonates with the vibration frequency of the ultrasonic vibrator 42 and generates a vertical vibration at its lower end.

[0080] The ultrasonic horn 40 is supported by the frame member 44 at a position that becomes a node of a standing wave having a resonance frequency. The frame member 44 is formed so as to surround the side and upper side of the ultrasonic horn 40, and the pressing force of the pressurizing portion 36 is applied to the upper surface of the frame member 44. The pressure F (load) of the pressurizing part 36 is detected by a pressure sensor 46 using a load cell or the like. The pressurizing force F detected by the pressure sensor 46 is input to the pressurizing control unit 48, and the pressurizing control unit 48 performs feedback control of the pressurizing force F of the pressurizing unit 36. The ultrasonic horn 40 is provided with heating means 43 made of an electric heater or the like. The temperature of the heating means 4 3 is detected by a temperature sensor (not shown) and is input to the temperature control section 32. The temperature control section 3 2 performs feedback control of the temperature T of the heating means 43. The ultrasonic vibrator 42 is driven and controlled at a predetermined frequency by the vibration control unit 50. 5 2 is a control device that controls each part, such as position control unit 24, suction control unit 30, temperature control unit 32, pressurization control unit 48, vibration control unit 50, etc. Send signals to control the whole. In general, a heat insulating portion (not shown) that does not transfer heat from the heating means 43 to the ultrasonic vibrator 42 is provided between the ultrasonic horn 40 and the ultrasonic vibrator 42. Is provided.

[0081] The operation of this connection apparatus will be described. First, the lower rigid printed wiring board (second wiring board) 3 is set on the mounting table 2 2 in the state shown in FIG. Also, the flexible printed wiring board (first wiring board) 1 is adsorbed to the lower surface of the holding plate 28 of the supply means 26 above. In this state, the position control unit 24 controls the position of the table 20 and the supply means 26 so that the connection terminals 2 and 4 of the both printed wiring boards 1 and 3 are parallel to the longitudinal direction and overlap each other. To do.

[0082] Next, the pressurizing unit 36 lowers the frame member 4 4 of the vibration means 3 8 and lowers the lower end surface of the ultrasonic horn 40 on the overlapping portion of the connection terminals 2 and 4 of both wiring boards 1 and 3. Press against the top surface of the flexible printed wiring board 1 so that it is positioned. The ultrasonic transducer 42 is activated while controlling the pressure F to the set pressure and the temperature T to the set temperature. In this way, the connection terminals 2 and 4 are solid-phase metal bonded under the uncured state of the resin film 6 by applying a set pressure while applying ultrasonic vibrations in the vertical direction mainly to the joints of both wiring boards 1 and 3. Is done.

[0083] This joining time is extremely short (about 0.5 seconds). After that, while the resin film 6 is in an uncured state, the pressurizing part 36 raises the vibration means 3 8 and the ultrasonic horn 40 is turned on. Separate from the top surface of the flexible printed wiring board 1. Here, the supply means 26 and the suction holding plate 28 are separated from the flexible printed wiring board 1 and are ready to supply the next flexible printed wiring board 1. The flexible printed wiring board 1 is transferred from the table 20 by another transfer means in a state of being joined to the rigid printed wiring board 3, and is carried out to the next process. Then, the resin film 6 is cured by a predetermined procedure corresponding to the resin film 6.

In this example, the flexible printed wiring board 1 is adsorbed to the holding plate 2 8 of the conveying means 26 by adopting an adsorbing structure. However, the holding means 28 8 is provided with a holding means so that the flexible printed wiring board 1 is attached. You may make it pinch.

In this embodiment, after both printed wiring boards are positioned on the mounting table 22 In addition, since the ultrasonic vibration and pressure are applied by the vibration means 3 8 and the pressure means 3 4 on the mounting table 2 2 to join the two connection terminals, one pressurization and vibration are required after positioning. Both connecting terminals can be crimped and joined in the process.

[0084] Depending on the adhesive resin used, when the connection terminal is connected in a single pressurization and vibration process, the resin is not sufficiently discharged into the space between terminals 2 and 2 and the space between terminals 4 and 4 The resin may harden. In such a case, crimping after positioning can be performed in two stages, temporary crimping and permanent crimping. In this case, pressurize the ultrasonic horn 40 to both positioned printed wiring boards, and at the same time, heat the adhesive resin to develop or maintain adhesiveness, so that both printed wiring boards are not easily detached. Temporarily crimp. After that, the pressurizing means and the vibration means are controlled so that sufficient pressure and ultrasonic vibration are applied to both the pre-crimped printed wiring boards for solid-phase metal bonding, and the main crimping of both connecting terminals is performed. Do. By pre-bonding without applying ultrasonic vibration, the adhesive resin is discharged into the space between terminals 2 and 2 and terminals 4 and 4 without curing. This ensures that terminals 2 and 4a are in full contact during the final crimping process, and solid-phase metal bonding between the terminals is ensured.

Example 4

[0085] Temporary pressure bonding after positioning of the printed wiring board and main pressure bonding for solid-phase metal bonding can be performed by separate devices. FIG. 7 (A) is a conceptual diagram of the temporary crimping apparatus 100, and FIG. 7 (B) is a conceptual diagram of the final crimping apparatus 110. The same members as those in the connection device of FIG. 6 are denoted by the same reference numerals, and detailed description thereof is omitted. The temporary crimping apparatus 100 includes positioning means including a positioning table 20 and a supply means 26, but the pressurizing means 3 4 A has no vibration means, and the pressurizing head 50 is printed. Pressurize wiring boards 1 and 3. The crimping device 110 has substantially the same configuration as the connection device of FIG. 6, the pressurizing means 34 B includes the vibration means 38, and the ultrasonic horn 40 B is connected to the printed wiring boards 1, 3. Apply ultrasonic vibration while pressurizing the joint. The pressure head 50 is provided with a heating means 4 3 A, and the ultrasonic horn 40 B is provided with a heating means 4 3 B.

[0086] First, in the same manner as in Example 3, the flexible printed wiring is provided by the supply means 26. Position and superimpose board 1 on the rigid blind wiring board (second wiring board) on the mounting table 2 2 of the temporary crimping device 100. Then, the pressure head 50 is lowered and a predetermined load and temperature are applied to the connection terminal portion where both wiring boards are overlapped. This load and temperature are such that the adhesive resin exhibits such a degree of stickiness that both wiring boards cannot be easily separated.

In this way, both the wiring boards 1 and 3 on which the temporary crimping portions are formed are transferred to the main pressure bonding device 110 by a transfer means (not shown). In the present crimping apparatus, both the wiring boards 1 and 3 are positioned and placed on the mounting table 2 2 B of the positioning table 20 B so that the pre-crimped terminal joint is in a predetermined position. Thereafter, the ultrasonic horn 40 B is lowered, and the temporary pressure-bonding portion is heated and pressurized, and ultrasonic bonding is applied to perform final pressure bonding. By doing so, the contact portions of the connection terminals of both wiring boards are solid-phase metal bonded.

Example 5

[0087] In each of the above-described Examples 1 to 4, the ladder-type (comb-toothed, structured-type adder type) connecting terminal 4 shown in Figs. The child 2 (Fig. 2) is joined. However, the connection terminal suitable for the present invention is not limited to this.

FIGS. 8 to 12 are diagrams showing other embodiments of ladder-type terminals. Since the two connection terminals provided on the two wiring boards may be reversed, one connection terminal will be referred to as the first terminal and the other as the second terminal.

In the embodiment shown in FIG. 8, the first terminal 60 is a ladder type and the second terminal 62 is a straight type, but an arc is formed between the child terminals 60a of the first terminal 60. It is a thing. In actual etching, the shape shown in Fig. 8 is obtained instead of the rectangle shown in Fig. 1A. This shape changes depending on the film thickness of the conductor (copper foil thickness).

In the embodiment shown in FIG. 9, the child terminal 60 Aa of the first terminal 60 A has a sawtooth shape. In consideration of the change in shape due to etching, this is approximately triangular in advance. The second terminal 6 2 A is a linear type.

[0091] The embodiment shown in FIG. 10 is a ladder type in which a child terminal 6 0 Ba of the first terminal 60 0 B is connected at predetermined intervals by two longitudinal portions 6 0 B b parallel to the longitudinal direction. What It is. In other words, the blank patterns 60 B c removed by etching are arranged in the longitudinal direction, and the straight second terminals 62 B run vertically through the blank patterns 60 B c. In FIG. 10 (A), this blank pattern 60 B c is a rectangle, FIG. 10 (B) is a circle or an ellipse, and FIG. 10 (C) is a diamond.

[0092] Fig. 1 1 shows that the first terminal 60C and the second terminal 62C are of the same cantilever ladder type (comb type), and each of the child terminals 60Ca and 62Ca are face-to-face joined together. is there. In Fig. 12, the first terminal 60D and the second terminal 62D are provided with sub-arc-shaped child terminals 6ODa and 62Da that protrude from the one side in the longitudinal direction to the side at predetermined intervals. The slave terminals 60Da and 62Da are stacked facing each other and joined.

Example 6

In the embodiment of FIG. 13, the first terminals 60 E and 6 OF are formed in a substantially waveform (zigzag shape). Fig. 13 (A) shows the second terminal 62E in a straight line. In FIG. 13B, the second terminal 62F is made into a waveform having the same cycle as that of the first terminal 60F, and both terminals 60F and 62F are joined at a number of positions apart in the longitudinal direction.

Example 1

The embodiments shown in the plan view and the cross-sectional view in FIGS. 14 to 16 are each a discontinuous land type in which lands such as via holes are arranged. The first terminal 60 G shown in FIG. 14 is formed by arranging the lands of the non-through via holes 68 connected to the linear inner layer circuit pattern 66 of the rigid blind wiring board 64 along the straight line on the upper surface.

[0095] The second terminal 62G provided on the flexible printed wiring board 70 has a linear shape that cuts through these land, that is, the first terminal 60G. These first and second terminals 60G and 62G are solid-phase metal bonded with an adhesive resin 72 interposed therebetween, and the resin 70 is solidified and fixed.

[0096] The first terminal 60H shown in FIG. 15 replaces the non-through via hole 68 shown in FIG. 14 with a through via hole 68A penetrating the rigid blind wiring board 64A. The land is used. According to this embodiment, since the adhesive resin 72 enters deeply into the via hole 6 8 A, the linear second terminal 60 0 H of the wiring board 6 4 A and the flexible printed wiring board 70 are used. Bond strength between terminals 6 2 H increases.

In the embodiment shown in FIG. 16, the first terminal 60 0 I of the rigid printed wiring board 6 4 B is linear, while the flexible printed wiring board 7 OA is a second line composed of lands arranged linearly. Terminal 6 2 I is formed. In other words, the flexible printed wiring board 7 forms a linear wiring pattern 74 on the upper surface of the OA, and lands 6 2 I connected to the wiring pattern 74 are provided on the lower surface, and the lands are arranged discontinuously on the straight line. It was.

Example 8

[0098] In the embodiment shown in Fig. 17, a linear first terminal 60 0 J provided on a rigid printed wiring board 6 4 C has a large number of recesses 76 and projections 78 extending in the width direction. It is an etching step type formed by etching so as to be alternately arranged in the direction. The second terminal 6 2 J of the flexible printed wiring board 70 B is linear.

Claims

The scope of the claims

[1] In a method of connecting printed wiring boards in which at least one wiring board is a flexible printed wiring board, the connection terminals of two printed wiring boards are connected to each other in the longitudinal direction, and the following steps a) to c) A method of connecting a printed circuit board, comprising:

a) Prepare a first printed wiring board and a second printed wiring board on which connection terminals are formed so as to overlap with the connection terminals of the first printed wiring board at a plurality of locations separated in the longitudinal direction;

[2] The printed wiring board connection method according to claim 1, wherein the adhesive resin is cured after step c).

[3] The following step d) is provided after step c):

2 printed wiring board connection method:

Step d) Release the pressure of the adhesive resin, and then cure the adhesive resin

[4] In step b), pressure is applied to both connection terminals of both printed wiring boards to perform temporary crimping;

5. The step c) is characterized in that the main press bonding is performed by applying ultrasonic vibration to both pre-bonded printed wiring boards while applying ultrasonic vibration, and joining the connecting terminals at a plurality of positions by solid-phase metal bonding. How to connect printed wiring boards.

5. The method for connecting printed wiring boards according to claim 1, wherein the adhesive resin is a thermoplastic resin.

[6] The printed wiring board connection method according to claim 5, wherein in step c), the thermoplastic resin is heated so as to be softened.

[7] The method for connecting printed wiring boards according to claim 6, further comprising the following step d_1) after step c): Step d— 1) Release the pressure on the thermoplastic resin, and then lower the temperature to cure the thermoplastic resin.

[8] The method of connecting a printed wiring board according to claim 7, wherein in step d-1), the pressure applied to the thermoplastic resin is released when the thermoplastic resin exhibits a strength of approximately 50% of its maximum adhesive strength. .

[9] The method for connecting printed wiring boards according to claim 5, wherein, in step b), the printed circuit boards are temporarily crimped by heating so that the thermoplastic resin is softened.

10. The method for connecting printed wiring boards according to claim 1, wherein the adhesive resin is a thermosetting resin.

[11] The method for connecting printed wiring boards according to claim 10, further comprising the following step d_2) in which the thermosetting resin is heated to a state in which the adhesiveness can be maintained in step c):

Step d— 2) Release the pressure on the thermosetting resin, then raise the temperature to cure the thermosetting resin.

[12] In step b), both printed wiring boards are temporarily pressed by heating to a state where the adhesiveness is maintained;

In step c), pressure bonding is applied to both printed wiring boards while applying ultrasonic vibration while the thermosetting resin is in an uncured state, and final bonding is performed in which the connection terminals are joined between solid phase metals at a plurality of locations;

The method for connecting printed wiring boards according to claim 10, wherein the temperature is then raised to cure the thermosetting resin.

[13] In step b), both printed wiring boards are pre-pressed by heating to a state where the adhesiveness is maintained;

The purine according to claim 10, further comprising the following step d_2): Wiring board connection method:

Step d-2) Release the pressure on the thermosetting resin, and then raise the temperature to cure the thermosetting resin.

[14] The printed wiring according to claim 13, wherein in step d-2), the pressure applied to the thermosetting resin is released when the thermosetting resin exhibits a hardness of approximately 50% of its maximum curing degree. Board connection method.

[15] The printed wiring board connection method according to claim 13, wherein in step d-2), the thermosetting resin is heat-cured using a heating furnace.

[1 6] The method for connecting printed wiring boards according to claim 10, wherein in step c), at least one of the connection terminals of both printed wiring boards is heated to a temperature lower than the melting temperature of the connection terminals and the thermosetting resin is not cured. .

[1 7] The printed wiring board connection method according to claim 1, wherein in step c), the ultrasonic vibration is applied in a direction substantially perpendicular to the joint surface of both connection terminals.

18. The method for connecting printed wiring boards according to claim 1, wherein in step c), the ultrasonic vibration is applied in a substantially horizontal direction with respect to the joint surfaces of both connection terminals.

[19] The connection terminal of the second printed wiring board is a ladder type provided with a plurality of child terminals provided separately in the longitudinal direction of the connection terminal;

2. The printed wiring board connection method according to claim 1, wherein in step b), the connection terminals are aligned so that the plurality of child terminals separately overlap the connection terminals of the first printed wiring board.

[20] The connection terminal of the second printed wiring board is a waveform;

2. The printed wiring board connection method according to claim 1, wherein in step b), the connection terminals of the first printed wiring board are aligned with each other so that the connection terminals of the first printed wiring board overlap each other at predetermined intervals.

[21] The connection terminal of the second printed wiring board is a discontinuous land type in which the land connected to the circuit pattern is arranged on the surface of the wiring board;

The method of connecting printed wiring boards according to claim 1, wherein in step b), the connection terminals are aligned so that the connection terminals of the first printed wiring board overlap each land. Law.

[22] The connection terminal of the second printed wiring board is a step type formed by etching so that a large number of concave portions and convex portions crossing in the width direction thereof are aligned in the longitudinal direction; in the step b), 2. The printed wiring board connection method according to claim 1, wherein the connection terminals are aligned so that the connection terminals of the first printed wiring board overlap each convex portion.

[23] In a printed wiring board connection device in which connection terminals of two printed wiring boards in which at least one wiring board is a flexible printed wiring board are overlapped and connected to each other in the longitudinal direction:

The first connection terminal of the first printed wiring board and the second connection terminal of the second printed wiring board in which the second connection terminal is formed so as to overlap with the first connection terminal at a plurality of locations divided in the longitudinal direction. Pressing means for pressing from above the joints of the two connection terminals, which are stacked with an adhesive resin between them;

Vibration means for applying ultrasonic vibration to the joint of both connection terminals;

It is characterized by comprising a control means for operating the pressurizing means and the vibration means at the same time and applying ultrasonic vibration while pressurizing both connection terminals in a state where the adhesive resin is uncured and joining the solid phase metal. A printed wiring board connecting device.

[24] The claim, wherein the control means controls the pressurizing means so as to release the pressurization in a state where the adhesive resin is uncured after the connection terminals are joined between the solid-phase metals. 2 3 Printed wiring board connection device.

[25] Furthermore, the first printed wiring board and the second printed wiring board are sandwiched between the connecting terminals, and the second connecting terminal is divided into the first connecting terminal and its longitudinal direction. The printed wiring board connecting device according to claim 23, further comprising positioning means for holding the plurality of overlapping portions.

[26] The positioning means supports the second printed wiring board from below and is capable of positioning on a horizontal plane, and supplies the first printed wiring board above the second printed wiring board. Connect the printed circuit board connection terminals in the longitudinal direction. 26. The printed wiring board connecting device according to claim 25, further comprising a supply means for holding the same in an overlapping manner

27. The vibration means includes an ultrasonic horn and an ultrasonic vibrator attached to the ultrasonic horn, and the pressurizing means pressurizes both printed wiring boards via the ultrasonic horn. 3, printed wiring board connection device.

28. The ultrasonic horn includes heating means for heating both connection terminal joints to a temperature that enables solid-phase metal joining in a state where the adhesive resin is uncured.

7, Printed wiring board connection device.

29. The printed wiring board connecting device according to claim 28, wherein the control means controls the heating means.

[30] The vibration means and the pressurizing means are characterized in that both the connection terminals are joined by applying ultrasonic vibration and pressure to both printed wiring boards held in an overlapping manner on the positioning means. Item 2 4 Printed wiring board connector.

[31] The vibration means includes a heating means for heating the adhesive resin;

The controller controls the positioning means to position the second connection terminal so as to overlap with the first connection terminal at a plurality of locations separated in the longitudinal direction, and then controls the pressure means and the heating means to bond. Apply pressure while heating the resin for developing or maintaining adhesiveness, and temporarily press the two printed wiring boards so that they do not easily come off.

Thereafter, the heating means, the pressure means, and the vibration means are controlled to apply pressure and ultrasonic vibration sufficient for solid-phase metal bonding to both pre-bonded printed circuit boards to The printed wiring board connecting device according to claim 24, wherein the crimping is performed.

[32] The connecting device includes a temporary crimping device and a main crimping device;

Temporary crimping equipment

The positioning means;

Temporary pressure bonding is applied to the connection terminals of both printed wiring boards positioned by the positioning means by applying heat and pressure to the extent that the adhesive resin can develop or maintain adhesiveness. Heating and pressurizing means,

This crimping device

It comprises the vibration means and the pressurizing means, and ultrasonic wave vibration and pressure are applied to both printed wiring boards that have been positioned and provisionally pressure-bonded conveyed from a temporary pressure bonding device, and both connection terminals are joined. The printed wiring board connecting device according to claim 24.

33. The printed wiring board connection device according to claim 23, wherein the vibration means applies ultrasonic vibration mainly in a direction perpendicular to the wiring board to both connection terminal joints.

34. The printed wiring board connection device according to claim 23, wherein the vibration means applies ultrasonic vibration mainly in a horizontal direction of the wiring board to both connection terminal joints.

35. The printed wiring board connection device according to claim 23, wherein a low friction material is interposed between the vibration means and the connection terminal joints in parallel with the joints.