TWI735651B - Copper foil and copper clad laminated board with the copper foil - Google Patents

Abstract

The object of the present invention is to provide a copper foil and a copper-clad laminate using the copper foil, which can achieve excellent adhesion, transmission characteristics, and heat resistance.

A copper foil characterized in that the roughness pattern is determined by the pattern method specified in JIS B0631:2000, and when the number of undulations Wn and the average depth R of the roughness pattern calculated from the roughness pattern are used to express the characteristics of the bonding surface of the copper foil, The number of undulations Wn is 11 to 30/mm, and the average depth R of the roughness pattern is 0.20 to 1.10 μm.

Description

Copper foil and copper clad laminated board with the copper foil

The invention relates to a copper foil and a copper-clad laminated board having the copper foil.

In recent years, the miniaturization and thinning of electronic equipment has been developed. In particular, various electronic components used in communication equipment such as servers, antennas, and mobile phones use highly integrated, small and high-density built-in electronic components. IC or LSI of printed wiring board.

To cope with this situation, high-density circuit wiring patterns such as multilayer printed wiring boards for high-density mounting and flexible printed wiring boards used in these devices (hereinafter sometimes referred to as printed wiring boards) are also required to be high-density. The demand for so-called fine-patterned printed wiring boards with circuit wiring patterns with fine circuit wiring widths and intervals has increased.

In the past, the copper foil used in printed wiring boards has a roughened surface on the side of the resin substrate by thermocompression bonding. The roughened surface exerts a fixing effect on the resin substrate and improves the resin substrate and copper. The bonding strength of the foil ensures the reliability as a printed wiring board (for example, Patent Document 1).

However, in order to increase the information processing speed of electronic equipment and support wireless communication, electronic components are required to be capable of high-speed transmission of electrical signals, and the application of high-frequency substrates has also been developed. For high-frequency-supporting substrates, in order to achieve high-speed transmission of electrical signals, it is necessary to reduce transmission loss. In addition to lowering the dielectric constant of the resin base material, it is also required to reduce the transmission loss of the circuit wiring as the conductor. Especially in the high frequency region exceeding several GHz, the skin effect causes the current flowing in the circuit wiring to concentrate on the surface of the copper foil. Therefore, when the copper foil that has been subjected to the previous roughening treatment is used for the substrate supporting high frequency, the skin effect The transmission loss of the chemical processing unit is large, and there is a problem that the transmission characteristics deteriorate.

In order to eliminate the above-mentioned problems, the following method has been discussed in the past: as a copper foil used in a printed wiring board supporting fine patterns and high frequency, a smooth copper foil that has not been roughened is used, and the copper foil is covered with a resin It is used on a substrate (for example, Patent Documents 2 to 4).

Here, as a method of reducing the surface roughness of the copper foil, a method of electroplating the surface of the copper foil after foil production with an electrolytic plating bath to which a gloss agent is added is known (Patent Document 5). In addition, as a method of obtaining a copper foil having a moderate surface roughness, a method of forming a roughened particle layer by pulse electrolysis is known (Patent Document 6).

However, although these smooth copper foils and finely roughened copper foils are excellent in the formability of fine pattern circuits and the transmission characteristics in the high-frequency region, it is difficult to stably and sufficiently improve the adhesion between the copper foil and the resin substrate. In particular, when such a smooth copper foil is used, there is a problem in that the thermal load during the manufacturing process and use of the printed wiring board further reduces the adhesion between the copper foil and the resin substrate. For this reason, in the past, the roughening of the copper foil was usually optimized to achieve both the transmission characteristics and the adhesion between the copper foil and the resin substrate.

On the other hand, in recent years, the manufacture of high-multilayer high-frequency substrates with more than 30 layers has begun, and the complexity of the manufacturing process caused by the high-multilayering has led to the gradual diversification of defects. Especially in the reflow process when various electronic components are mounted on the printed wiring board, not only the delamination (heat-resistant expansion) between the resin and the copper foil occurs frequently, but also the delamination between the resin and the resin occurs frequently. This kind of delamination between resin and resin is recognized as a phenomenon in which exhaust gas generated by the decomposition of the resin during heating accumulates between the resin and the resin, and an increase in exhaust pressure causes delamination. The resin surface of the bonding surface between the resin and the resin has the replication shape of the copper foil surface. The shape of the copper foil surface affects the difficulty of delamination. Therefore, in order to suppress the delamination between the resin and the resin, it is suitable to have a suitable replication shape. The surface shape of the copper foil is very important. However, in the conventional finely roughened copper foil and smooth copper foil that are expected to achieve low transmission loss, the delamination between the resin and the resin cannot be sufficiently suppressed. In addition, delamination between the resin and the resin may be caused by the destruction of the interface between the resin and the copper foil due to the increase in heating temperature, and it is also the main reason for the circuit wiring to peel off from the resin substrate. Therefore, particularly in printed wiring boards where the bonding surface of circuit wiring (copper foil) and the resin substrate is positively small and supports fine patterns, the problem of reduction in yield due to such delamination has become serious, and improvement in heat resistance is required.

【Advanced Technical Literature】 【Patent Literature】

Patent Document 1: Japanese Patent Laid-Open No. 5-029740

Patent Document 2: Japanese Patent Laid-Open No. 2003-023046

Patent Document 3: Japanese Patent Laid-Open No. 2007-165674

Patent Document 4: Japanese Patent Laid-Open No. 2008-007803

Patent Document 5: Japanese Patent Laid-Open No. 9-272994

Patent Document 6: Japanese Patent Laid-Open No. 2011-162860

The present invention was developed in view of the foregoing facts, and its object is to provide a copper foil and a copper-clad laminate having the copper foil, which can achieve excellent adhesion, transmission characteristics, and heat resistance.

In the conventional copper foil, from the viewpoint of reducing the transmission loss, a smooth copper foil surface with less unevenness is required. In addition, from the viewpoint of adhesion to the resin and improvement of heat resistance, it is required to have a rough shape and a large surface area in contact with the resin. These are common technical knowledge on the surface of the copper foil. From these viewpoints, the surface shape of the copper foil is usually adjusted by the irregularities formed by small roughening particles of about 0.01 to 1 μm. In addition, the evaluation indexes Ra (arithmetic average roughness) and Rz (ten-point average roughness) of copper foil surface shape commonly used in the past do not include the length of each mountain shape of the copper foil surface and the unit length due to the calculation principle. Information such as the number of mountain shapes, or the depth of each mountain shape, etc., these indicators are difficult to describe in more detail the influence of the copper foil surface shape on the resin adhesion, heat resistance, and transmission loss for printed wiring boards that require higher performance. To evaluate. Therefore, the conventional copper foil evaluated by the above-mentioned index did not consider the influence of the undulation of the copper foil surface, and there was a problem that sufficient transmission loss characteristics could not be obtained, or sufficient heat resistance could not be obtained.

In contrast, the inventors of the present invention conducted intensive research on the irregularities on the surface of copper foil, focusing on relatively macroscopic irregularities such as undulations, rather than the fine (microscopic) irregularities that are excellent in anchor effect in the past, and found that The roughness pattern is determined by the pattern method specified in JIS B0631: 2000, and the number of undulations Wn and the roughness pattern average depth R calculated from the roughness pattern can further reduce the transmission loss in the high-frequency region compared to the past situation such as at 40 GHz. It also improves the adhesion and heat resistance with the resin, showing a close relationship. Based on these findings, it was found that the copper foil surface has a long wave length of about tens to hundreds of μm, and the depth is controlled to a shallower shape of about 0.2 to 1.1 μm, which can be caused by the rough surface of the copper foil. When the transmission loss of the temperature is kept small, the adhesion to the resin layer and the heat resistance are both improved very well, and the present invention has been completed. This invention controls the number of undulations Wn and the average depth R of the roughness pattern on the bonding surface of the copper foil to a specified range, so that, for example, when a printed wiring board is formed, the adhesion between the copper foil and the resin can be improved, and The deterioration of the transmission characteristics is suppressed, and the delamination between the resin and the resin during heating can also be effectively suppressed.

That is, the main configuration of the present invention is as follows.

[1] A copper foil characterized in that the roughness pattern is determined by the pattern method specified in JIS B0631:2000, and the number of undulations Wn and the average depth of the roughness pattern calculated from the roughness pattern are used to represent the bonding surface of the copper foil. In the feature, the number of undulations Wn is 11 to 30/mm, and the average depth R of the roughness pattern is 0.20 to 1.10 μm.

[2] The copper foil according to the above [1], wherein the number of undulations Wn is 12 to 27/mm, and the average depth R of the roughness pattern is 0.30 to 0.90 μm.

[3] The copper foil according to the above [2], wherein the number of undulations Wn is 14 to 22/mm, and the average depth R of the roughness pattern is 0.40 to 0.80 μm.

[4] The copper foil according to any one of the above [1] to [3], wherein the surface area ratio of the measured three-dimensional surface area of the bonding surface to the two-dimensional surface area measured on a plane is 1.05 to 2.85.

[5] The copper foil according to the above [4], wherein the surface area ratio of the measured three-dimensional surface area of the bonding surface to the two-dimensional surface area when measured on a flat surface is 2.00 to 2.70.

[6] The copper foil according to any one of [1] to [5] above, wherein the copper foil is an electrolytic copper foil.

[7] The copper foil according to any one of [1] to [6] above, wherein the bonding surface is a rough surface.

[8] The copper foil according to any one of [1] to [7] above, wherein the copper foil is provided with a copper foil base and the copper foil base on the bonding surface side. A surface-treated copper foil with a surface treatment layer on the surface, the surface treatment layer contains at least one layer of a roughened particle layer, a nickel surface treatment layer, a zinc surface treatment layer, a chromium surface treatment layer, and a silane coupling agent layer, the bonding The surface is the outermost surface of the surface treatment layer.

[9] The copper foil according to the above [8], wherein the surface treatment layer contains the nickel surface treatment layer, and the adhesion amount of nickel is 0.010 to 0.800 mg/dm ² .

[10] The copper foil according to the above [9], wherein the adhesion amount of the nickel is 0.020 to 0.400 mg/dm ² .

[11] The copper foil according to any one of [8] to [10] above, wherein the surface treatment layer contains the chromium surface treatment layer, and the adhesion amount of chromium is 0.010 to 0.300 mg/dm ² .

[12] The copper foil according to the above [11], wherein the adhesion amount of the chromium is 0.015 to 0.200 mg/dm ² .

[13] A copper clad laminate comprising the copper foil described in any one of [1] to [12] above, and an insulating substrate adhesively laminated on the adhesive surface.

According to the present invention, it is possible to provide a copper foil and a copper-clad laminate having the copper foil, which can achieve excellent adhesion, transmission characteristics, and heat resistance.

FIG. 1 is a graph showing the relationship between the average depth R of the roughness pattern and the number of undulations Wn of the copper foil of the present invention and the conventional copper foil (previous example A).

Fig. 2 is a schematic cross-sectional view showing a manufacturing procedure of the test piece T2 when the reflow heat resistance test is performed in the example.

<Copper Foil>

Hereinafter, preferred embodiments of the copper foil of the present invention will be described in detail.

The copper foil of the present invention is characterized in that the roughness pattern is determined by the pattern method specified in JIS B0631: 2000, and the number of undulations Wn calculated from the roughness pattern and the average depth R of the roughness pattern are used to represent the bonding surface of the copper foil. In the feature, the number of undulations Wn is 11 to 30/mm, and the average depth R of the roughness pattern is 0.20 to 1.10 μm.

In the present invention, the bonding surface refers to the outermost surface of the copper foil, which is the surface used for bonding and laminating the resin substrate. In addition, the bonding surface of the copper foil is at least one of the surfaces of the copper foil, or both surfaces. In addition, in the present invention, unless otherwise specified, copper foil includes electrolytic copper foil, rolled copper foil, and surface-treated copper foil having surface-treated these copper foils, and the like. Therefore, for example, when the copper foil of the present invention is a surface-treated copper foil including a copper foil base and a surface treatment layer on the surface of the copper foil base, the adhesion surface of the copper foil is the outermost surface of the surface treatment layer.

With regard to the unevenness of the copper foil surface, the inventors focused on the macroscopic surface properties called "undulations" and found that controlling the undulation characteristics on the bonding surface of the copper foil can achieve high-level transmission characteristics and heat resistance that were not available in the past. Thus, the present invention has been completed.

In the present invention, when evaluating the undulation of the bonding surface of the copper foil, the graphic parameters specified in JIS B 0631:2000 are introduced. The graph refers to the part of the curve sandwiched by two partial mountains, which is expressed by graph length and graph depth. In particular, in the present invention, the roughness pattern average length AR and the roughness pattern average depth R measured under the measurement conditions described later are evaluated.

Here, the roughness pattern average length AR is the arithmetic average _{of the roughness pattern length AR i obtained by the evaluation length.} That is, it is represented by the following numerical formula (1).

In the above formula (1), n is the number of roughness patterns (equal to the number of _{AR i).} In addition, the roughness pattern length AR _i is a length of A or less.

In addition, the roughness pattern average depth R is an arithmetic average _{of the roughness pattern depth H j obtained by the evaluation length.} That is, it is represented by the following formula (2).

[Numerical formula 2]

In the above formula (2), m is the number _{of H j.}

The specific measurement was performed under the following conditions.

First, the bonding surface of the copper foil is in the TD direction (vertical to the longitudinal direction of the copper foil (corresponding to the foil making direction)) within a certain range (for example, a linear range with a length of 50 mm) in accordance with JIS B 0631: 2000 Measure the average length AR of the roughness pattern and the average depth R of the roughness pattern. The measuring device may be any device capable of measuring in accordance with the above-mentioned JIS standard, and for example, a surface roughness measuring machine (Surfcorder SE3500, manufactured by Kosaka Laboratory Co., Ltd.) or the like can be used. In addition, the measurement conditions are based on the recommended measurement conditions of the above-mentioned JIS standards, and are A=0.1mm, B=0.5mm, ln=3.2mm, and λs=2.5μm.

In the present invention, the number of undulations Wn (pieces/mm) is calculated by the following formula (3) based on the average length AR of the roughness pattern measured under the above-mentioned conditions.

Wn=1/AR...(3)

According to the above formula (3), the average number of fluctuations on the 1mm line is calculated.

On the bonding surface of the copper foil of the present invention, the number of undulations Wn is 11 to 30/mm. Control in the above range can achieve low transmission loss, high adhesion and excellent heat resistance. On the other hand, when the number of undulations Wn is less than 11/mm, the pressure at the resin-resin interface or the resin-copper foil interface cannot be sufficiently suppressed due to the exhaust gas generated by the resin (vaporization of low-molecular resin components due to heat). Since the delamination between layers spreads, the circuit wiring is easily peeled from the resin substrate, and the yield (heat resistance) is reduced. In addition, when the number of fluctuations Wn exceeds 30/mm, the skin effect causes high-frequency signals to easily flow on the surface of the copper foil, the signal propagation path is long, and the transmission loss increases. In particular, from the viewpoint of achieving excellent heat resistance and transmission characteristics, the number of fluctuations Wn is preferably controlled to be 12 to 27 per mm, and more preferably 14 to 22 per mm.

In addition, on the bonding surface of the copper foil of the present invention, the average depth R of the roughness pattern is 0.20 to 1.10 μm. By controlling the average pattern depth R together with the number of undulations Wn, it is possible to achieve both transmission characteristics and heat resistance at a high level beyond the past. On the other hand, when the average depth R of the roughness pattern is less than 0.20 μm, the propagation of delamination caused by the exhaust pressure generated by the resin cannot be sufficiently suppressed at the resin-resin interface or the resin-copper foil interface, so the circuit wiring is likely to be removed from the Peeling from the resin substrate reduces the yield (heat resistance). In addition, when the average depth R of the roughness pattern exceeds 1.10μm, the skin effect causes the high-frequency signal to easily flow on the surface of the copper foil, the signal propagation path is long, and the transmission loss increases. In particular, from the viewpoint of achieving excellent heat resistance and transmission characteristics, the roughness pattern average depth R is preferably controlled to be 0.30 to 0.90 μm, more preferably 0.40 to 0.80 μm.

In addition, as long as the number of undulations Wn and the average depth R of the roughness pattern are controlled within the specified range on the bonding surface bonded with the resin, the surface properties of other surfaces can be appropriately adjusted within the range that does not affect the effects of the present invention.

In addition, the measured three-dimensional surface area of the bonding surface of the copper foil of the present invention is preferably 1.05 to 2.85, and more preferably 2.00 to 2.70 relative to the surface area of the two-dimensional surface area when measured on a plane. The surface area ratio of this bonding surface is represented by the ratio (A/B) between the measured three-dimensional surface area A of the copper foil surface and the two-dimensional surface area B when it is projected on a plane and measured. In addition, the three-dimensional surface area A can be measured using, for example, a laser microscope (VK8500, manufactured by Keynes Co., Ltd.). In addition, the two-dimensional surface area B is an area corresponding to the measurement range of the three-dimensional surface area A when viewed in a plane from the surface of the copper foil.

It is generally known that the smaller the surface area ratio, the shorter the path for high-frequency signals to flow on the surface due to the skin effect, and the smaller the transmission loss. However, in the heat resistance test, the contact area between the resin and the copper foil or between the resin and the resin is small, so there is a problem that the heat resistance is reduced.

In contrast, in the copper foil of the present invention, the undulation characteristics of the bonding surface are controlled to a predetermined relationship as described above, so that the surface area ratio is controlled to be 1.05 or more and 2.85 or less. Therefore, the height difference between the undulating concave portion and the convex portion is small and thick. The current density in the electroplating process is uniform, and roughened particles of the same size are uniformly formed in the concave and convex portions, so that the adhesive force with the resin is uniform, and the heat resistance can be improved with low transmission loss. On the other hand, when the surface area ratio (A/B) is less than 1.05, the contact area between the resin and the copper foil or between the resin and the resin is small, and the heat resistance tends to decrease. In addition, when the surface area ratio (A/B) exceeds 2.85, the high-frequency flow path is long, and the transmission loss tends to increase.

In addition, the copper foil of the present invention is preferably an electrolytic copper foil. In the case of electrolytic copper foil, the glossy surface (S surface) is the surface in contact with the electrolytic drum, and the shape of the drum surface is replicated, and the influence of the replicated shape tends to impair the uniformity of roughening. On the other hand, the rough surface (also referred to as the roughened surface, M surface) is the surface on the electrolyte side during electrolysis, and the unevenness of the surface of the drum has disappeared, so it has a characteristic that the uniformity of the roughening treatment is excellent. Therefore, in the electrolytic copper foil, particularly on the rough surface, the number of undulations Wn and the average depth R of the roughness pattern are preferably controlled within the above-specified range.

In addition, the copper foil of the present invention is preferably a surface-treated copper foil provided with a copper foil base and a surface treatment layer on the surface of the copper foil base on the bonding surface side. In addition, the above-mentioned surface treatment layer preferably contains at least one layer of a roughened particle layer, a nickel surface treatment layer, a zinc surface treatment layer, a chromium surface treatment layer, and a silane coupling agent layer, and more preferably contains a nickel surface treatment layer and At least one of the chromium surface treatment layers more preferably has a multilayer structure composed of the above-mentioned layers. In this surface-treated copper foil, the bonding surface is the surface of the outermost layer of the surface-treated layer.

In addition, the surface treatment layer is a very thin area, so it will not affect the number of undulations Wn of the bonding surface and the average depth R of the roughness pattern. The undulation characteristics of the bonding surface of the surface-treated copper foil are substantially affected by the bonding surface The undulation characteristics of the surface of the copper foil substrate corresponding to the surface are determined. Therefore, the copper foil base of the surface-treated copper foil is preferably on the surface of the bonding surface side, the number of undulations Wn is 12 to 85/mm, and the average depth R of the roughness pattern is controlled to be 0.10 to 1.50 μm. In addition, the copper foil substrate may be any one of electrolytic copper foil and rolled copper foil.

In addition, the surface treatment layer contains a layer of roughened particles, so that the adhesion effect between the copper foil and the resin substrate increases. In addition, even if the resin substrate generates exhaust gas when heated in the reflow heat resistance test, the copper foil and The adhesiveness of the resin substrate is high, so it still has the effect of suppressing swelling (delamination), and the heat resistance, especially the heat resistance of reflow, is improved. The roughened particle layer is preferably formed as a roughened layer on the surface of the copper foil base. Such a roughened particle layer has the advantages of improving adhesion and heat resistance as described above. In addition, it also has the disadvantage of increasing the transmission loss due to the effect of the skin effect after the size of the roughened particles becomes larger. Therefore, it is preferable to appropriately adjust the particle size of the roughened particles.

In addition, the surface treatment layer contains at least one metal treatment layer of a nickel surface treatment layer, a zinc surface treatment layer, and a chromium surface treatment layer, thereby preventing the diffusion of copper and maintaining a high degree of adhesion between the copper foil and the resin substrate more stably. The manufacturing process of the printed wiring board includes a process accompanied by heating, such as a bonding process of resin and copper foil, and a soldering process. The heat received by these processes may cause the copper to diffuse to the resin side and reduce the adhesion between the copper foil and the resin. However, by providing a metal treatment layer containing nickel and chromium, the diffusion of copper can be effectively prevented. In addition, the metal treatment layer shown above can also function as a rust-preventing metal to prevent patina.

The nickel surface treatment layer is a metal treatment layer containing nickel, and is particularly preferably formed as a ground layer on the surface of the copper foil substrate or on the above-mentioned roughened particle layer. Here, the adhesion amount of nickel is preferably 0.010 to 0.800 mg/dm ² , more preferably 0.020 to 0.400 mg/dm ² . As shown above, the undulation characteristics of the copper foil substrate on the bonding surface side are controlled within a specified range, and the unevenness of the undulation is suppressed below a certain level. Therefore, when nickel plating is performed, a nickel layer with a uniform thickness can be formed , Compared with the past, heat resistance can be improved. On the other hand, when the amount of nickel deposited is less than 0.010 mg/dm ² , the amount of nickel is small, the effect of preventing copper diffusion is small, and the resin is likely to deteriorate, so there is a tendency for heat resistance (resin and copper foil) to decrease. In addition, when the deposited amount of nickel exceeds 0.800 mg/dm ² , the conductivity of nickel is lower than that of copper, so there is a tendency for the transmission loss to increase due to the influence of the skin effect.

The chromium surface treatment layer is a metal treatment layer containing chromium, and is preferably formed as an antirust treatment layer on the side closer to the bonding surface. Here, the adhesion amount of chromium is preferably 0.010 to 0.300 mg/dm ² , more preferably 0.015 to 0.200 mg/dm ² . As shown above, the undulation characteristics of the copper foil substrate on the bonding surface side are controlled within the specified range, and the unevenness of the undulation is suppressed below a certain level. Therefore, when the chrome plating process is performed, a chrome layer with a uniform thickness can be formed. Compared with the past, heat resistance can be improved. In addition, by treating the chromium on the surface layer, the surface is covered with chromium oxide and chromium hydroxide, and the rust prevention effect can be obtained. On the other hand, when the chromium adhesion amount is less than 0.010 mg/dm ² , the amount of chromium is small, the effect of preventing the diffusion of copper is small, and the resin is easily deteriorated, so there is a tendency for heat resistance (resin and copper foil) to decrease. In addition, when the adhesion amount of chromium exceeds 0.300 mg/dm ² , since chromium has a lower conductivity than copper, there is a tendency for the transmission loss to increase due to the influence of the skin effect.

The zinc surface treatment layer is a metal treatment layer containing zinc, and is particularly preferably formed as a heat-resistant treatment layer between the nickel surface treatment layer and the chromium surface treatment layer. Here, the adhesion amount of zinc is preferably 0.005 to 0.500 mg/dm ² , more preferably 0.010 to 0.400 mg/dm ² . With this zinc surface treatment layer, it has the advantages of preventing discoloration during heating, anti-rust effect, and improving heat resistance.

The silane coupling agent layer has the effect of chemically bonding the copper foil and the resin substrate, and is preferably formed as the outermost layer of the surface treatment layer. Here, in terms of silicon (Si) atoms, the adhesion amount of silane is preferably 0.0002 to 0.0300 mg/dm ² , more preferably 0.0005 to 0.0100 mg/dm ² . Having such a silane coupling agent layer can further improve the adhesion between the copper foil and the resin substrate.

In addition, the adhesion amount of the above-mentioned nickel, chromium, zinc, and silane can be measured by fluorescent X-ray analysis. The specific measurement conditions will be described in Examples described later.

The copper foil of the present invention can be suitably used as a copper-clad laminate. The copper clad laminate preferably has the copper foil of the present invention and an insulating substrate adhesively laminated on the adhesive surface. This type of copper clad laminate can produce circuit boards with high heat resistance and excellent high-frequency transmission characteristics, and has excellent effects. As an insulating substrate, a flexible resin substrate, a rigid resin substrate, etc. are mentioned, for example. In addition, the copper-clad laminated board of the present invention can be suitably used as a printed wiring board in particular.

<Method of manufacturing copper foil>

Next, a preferable manufacturing method of the copper foil of the present invention will be explained.

Hereinafter, an example of the manufacturing method of copper foil is demonstrated using electrolytic copper foil (or surface-treated electrolytic copper foil) as an example.

(1) Foil making

The electrolytic copper foil is manufactured by the following method: a sulfuric acid-copper sulfate aqueous solution is used as an electrolyte, and an insoluble anode composed of titanium coated with a platinum group element or its oxide element is placed between an insoluble anode made of titanium and a titanium cathode roller arranged opposite to the anode. The electrolyte is supplied, and a direct current is applied between the two electrodes while rotating the cathode drum at a constant speed, thereby depositing copper on the surface of the cathode drum, peeling the deposited copper from the surface of the cathode drum, and continuously winding it.

It is generally estimated that the number of undulations Wn and the average depth R of the roughness pattern depend on the composition of the electrolyte (for example, the concentration of added components and various components) and the electrolysis conditions (for example, current density, liquid temperature, flow rate, etc.). In particular, in the past common electrolytes, as additive components of electrolytes other than sulfuric acid and copper sulfate, for example, sodium 3-mercapto-1-propanesulfonate (MPS), hydroxyethyl cellulose (HEC), low Molecular weight glue (PBF), chlorine (Cl, such as NaCl added) and so on. However, the inventors of the present invention have studied the relationship between the composition of the electrolyte and the fluctuations, and found that when the electrolyte containing the above-mentioned additives is used to produce electrolytic copper foil, as shown in the previous example A of FIG. 1, the roughness pattern is reduced. After the average depth R, the number of fluctuations Wn increases, and the transmission loss characteristics cannot be sufficiently improved.

Therefore, after further research, it is found that in addition to the above-mentioned additives, additives such as sodium citrate, sulfamic acid, ammonia water, etc., which have the effect of forming complexes with copper ions to increase the electroplating overvoltage, can be used to improve the roughness. The state where the average pattern depth R is low reduces the number of fluctuations Wn (the present invention in FIG. 1). The principle of this phenomenon is not clear, but it can be inferred that sodium citrate, sulfamic acid, ammonia water and copper ions form complexes, resulting in an increase in electroplating overvoltage, as a result, the uniformity of the electroplating treatment increases, and the number of fluctuations W decreases. .

Based on the above findings, in the present invention, it is preferable to appropriately adjust the composition of the electrolytic solution used for foil production. Examples of the composition and electrolysis conditions of the electrolytic solution applied to the production of the electrolytic copper foil of the present invention are shown below. In addition, the following conditions are preferred examples, and the type and amount of additives, and electrolysis conditions can be appropriately changed and adjusted as needed within a range that does not affect the effects of the present invention.

(Foil-making conditions)

Copper sulfate pentahydrate... converted to copper (atoms), preferably 60 to 110 g/L, more preferably 60 to 90 g/L

Sulfuric acid...preferably 40 to 135g/L, more preferably 40 to 80g/L

MPS...preferably 1 to 10 mg/L, more preferably 2 to 3 mg/L

HEC...preferably 1 to 7 mg/L, more preferably 1 to 2 mg/L

PBF...preferably 3 to 9 mg/L, more preferably 3 to 4 mg/L

Sodium citrate...preferably 0-40g/L, more preferably 20-40g/L

Sulfamic acid...preferably 0 to 30 g/L, more preferably 10 to 20 g/L

Ammonia (ammonia concentration 30% by mass)...preferably 0 to 35 g/L, more preferably 10 to 25 g/L

Chlorine (Cl, as NaCl)...preferably 15 to 60 mg/L, more preferably 30 to 40 mg/L

Current density...preferably 35 to 60 A/dm ² , more preferably 40 to 50 A/dm ²

Liquid temperature...preferably 40 to 65°C, more preferably 50 to 60°C

Foil thickness...preferably 6 to 100μm, more preferably 6 to 65μm

(2) Homogenization treatment

Regarding the electrolytic copper foil manufactured as described above, after intensive research on the method to further moderately reduce the number of undulations Wn, it was found that an electrolytic bath with a strong leveling effect (treatment to reduce irregularities on the surface of the copper foil) was used for pulse current. Electrolysis can make the number of fluctuations Wn reach an appropriate value.

As an additive component of the electrolytic solution other than sulfuric acid and copper sulfate used in the electrolytic bath with such a strong homogenization effect, low molecular weight gum (PBF), coumarin, 1,4-butynediol, and the like can be cited. In addition, if the leveling effect is too strong, the reflow heat resistance tends to decrease. Therefore, it is preferable to maintain a balance with the reflow heat resistance and adjust the leveling effect appropriately.

In addition, regarding electrolysis using pulse current, it is preferable to set the pulse reverse electrolysis time (t _rev ) to be longer than the pulse forward electrolysis time (t _on ), and to set the pulse forward current density (I _on ) to be longer than the pulse reverse current The density (I _rev ) is high. Here, the forward current is the cathodic reaction of the surface of the copper foil being electroplated, and the reverse current is the anodic reaction of the surface of the copper foil being dissolved. It is estimated that the ratio of the reverse current that dissolves the surface of the copper foil is set high in the pulse current, so that the undulations on the surface of the copper foil are appropriately dissolved, and a copper foil having a moderate number of undulations Wn can be obtained.

Based on the above findings, in the present invention, it is preferable to appropriately adjust the composition and pulse current of the electrolytic solution used for the homogenization treatment. Examples of the composition and electrolysis conditions of the electrolytic solution suitable for the homogenization treatment of the present invention are shown below. In addition, the following conditions are preferred examples, and the type and amount of additives, and electrolysis conditions can be appropriately changed and adjusted as needed within a range that does not affect the effects of the present invention.

(Homogenization treatment conditions)

Copper sulfate pentahydrate... converted to copper (atoms), preferably 40 to 80 g/L, more preferably 60 to 75 g/L

Sulfuric acid...preferably 60 to 125g/L, more preferably 100 to 120g/L

PBF...preferably 0 to 800mg/L, more preferably 300 to 500mg/L

Coumarin...preferably 0 to 4g/L, more preferably 2.5 to 3.0g/L

1,4-Butynediol...preferably 0 to 3g/L, more preferably 1.0 to 2.0g/L

Chlorine (Cl, as NaCl)...preferably 20 to 55 mg/L, more preferably 30 to 40 mg/L

Electrolysis time... preferably 3 to 25 seconds, more preferably 5 to 20 seconds

Liquid temperature...preferably 30 to 70°C, more preferably 50 to 60°C

<Pulse condition>

Pulse electrolysis time (t _on )...preferably 0 to 30 milliseconds, more preferably 0 to 10 milliseconds

Pulse reverse electrolysis time (t _rev )...preferably 50 to 600 milliseconds, more preferably 200 to 300 milliseconds

Pulse electrolysis stop time (t _off )...preferably 0 to 40 milliseconds, more preferably 20 to 30 milliseconds

Pulse current density (I _on )...preferably 0 to 10A/dm ² , more preferably 0 to 6A/dm ²

Pulse reverse current density (I _rev )...preferably -15 to -50A/dm ² , more preferably -20 to -30A/dm ²

(3) Surface treatment

Furthermore, the electrolytic copper foil produced as described above can be used as a copper foil substrate, and surface treatments such as a roughened layer, a ground layer, a heat-resistant treatment layer, and a rust-proof treatment layer can be appropriately formed on the roughened surface as required. The layer can also be used as a surface-treated electrolytic copper foil. In addition, these surface treatment layers will not affect the undulation characteristics of the rough surface of the above-mentioned electrolytic copper foil, and the undulation characteristics of the outermost surface of the surface-treated electrolytic copper foil are substantially the same as those of the rough surface of the electrolytic copper foil used as the copper foil substrate. The fluctuation characteristics are the same. In addition, the surface treatment layer is not limited to the above-mentioned treatment layer, and a part or all of them may be appropriately combined, and may be combined with treatment layers other than the above.

Here, the roughening layer can be formed by a well-known method, for example, it is preferable to carry out by electroplating, and it is more preferable to carry out by a two-stage roughening electroplating process. This roughening plating treatment can be performed by appropriately adjusting it by a well-known method.

Examples of the composition and electrolysis conditions of the plating solution for roughening plating are shown below. In addition, the following conditions are preferred examples, and the type and amount of additives, and electrolysis conditions can be appropriately changed and adjusted as needed within a range that does not affect the effects of the present invention.

(Conditions for roughening plating treatment (1))

Copper sulfate pentahydrate... converted to copper (atoms), preferably 5 to 30 g/L, more preferably 10 to 20 g/L

Sulfuric acid...preferably 100 to 150g/L, more preferably 130 to 140g/L

Ammonium molybdate... converted to molybdenum (atom), preferably 1 to 6 g/L, more preferably 2 to 4 g/L

Cobalt sulfate heptahydrate... converted to cobalt (atom), preferably 1 to 5 g/L, more preferably 2 to 3 g/L

Ferrous sulfate heptahydrate... converted to iron (atom), preferably 0.05 to 5.0 g/L, more preferably 0.1 to 1.5 g/L

Current density...preferably 15 to 50 A/dm ² , more preferably 20 to 40 A/dm ²

Electrolysis time...preferably 1 to 80 seconds, more preferably 1 to 60 seconds

Liquid temperature...preferably 20 to 50°C, more preferably 30 to 40°C

(Conditions for roughening plating treatment (2))

Copper sulfate pentahydrate... converted to copper (atoms), preferably 10 to 80 g/L, more preferably 13 to 72 g/L

Sulfuric acid...preferably 20 to 150g/L, more preferably 26 to 133g/L

Current density...preferably 2 to 70A/dm ² , more preferably 3 to 67A/dm ²

Electrolysis time...preferably 1 to 80 seconds, more preferably 1 to 60 seconds

Liquid temperature...preferably 15 to 75°C, more preferably 18 to 67°C

In addition, the ground layer includes, for example, a nickel surface treatment layer containing nickel formed by a nickel plating treatment, a ground layer formed by a copper-zinc alloy electroplating treatment, a copper-nickel alloy electroplating treatment, and the like. These electroplating treatments can be appropriately adjusted and performed by a well-known method.

Examples of the composition and electrolysis conditions of the plating solution for nickel plating are shown below. In addition, the following conditions are preferred examples, and the type and amount of additives, and electrolysis conditions can be appropriately changed and adjusted as needed within a range that does not affect the effects of the present invention.

(Conditions for nickel plating)

Nickel sulfate... converted to nickel (atoms), preferably 3.0 to 7.0 g/L, more preferably 4.0 to 6.0 g/L

Ammonium persulfate...preferably 30.0 to 50.0 g/L, more preferably 35.0 to 45.0 g/L

Boric acid...preferably 20.0 to 35.0g/L, more preferably 25.0 to 30.0g/L

Current density...preferably 0.5 to 4.0 A/dm ² , more preferably 1.0 to 2.5 A/dm ²

Electrolysis time...preferably 1 to 80 seconds, more preferably 1 to 60 seconds

Liquid pH...preferably 3.5 to 4.0, more preferably 3.7 to 3.9

Liquid temperature...preferably 25 to 35°C, more preferably 26 to 30°C

As the heat-resistant treatment layer, for example, a heat-resistant treatment layer formed by a zinc surface treatment layer containing zinc formed by a zinc plating treatment, and the like can be cited. These electroplating treatments can be appropriately adjusted and performed by a well-known method.

Examples of the composition and electrolysis conditions of the plating solution for galvanizing treatment are shown below. In addition, the following conditions are preferred examples, and the type and amount of additives, and electrolysis conditions can be appropriately changed and adjusted as needed within a range that does not affect the effects of the present invention.

(Conditions for galvanizing)

Zinc sulfate heptahydrate... converted to zinc (atom), preferably 1 to 40 g/L, more preferably 1 to 30 g/L

Sodium hydroxide...preferably 8 to 350g/L, more preferably 10 to 300g/L

Current density...preferably 0.1 to 15A/dm ² , more preferably 0.1 to 10A/dm ²

Electrolysis time...preferably 1 to 80 seconds, more preferably 1 to 60 seconds

Liquid temperature...preferably 5 to 80°C, more preferably 5 to 60°C

As the anti-rust treatment layer, for example, a chromium surface treatment layer (inorganic anti-rust layer) containing chromium formed by chromium plating treatment, an organic anti-rust layer formed by organic anti-rust treatment such as benzotriazole treatment, and Anti-rust layer formed by silane coupling agent treatment, etc. These electroplating treatments can be appropriately adjusted by well-known methods.

The chromium plating treatment is performed by the following methods: dissolving CrO ₃ or K ₂ Cr ₂ O ₇ in water to prepare an aqueous solution, immersing the copper foil in the aqueous solution, washing and drying, or electrolyzing the copper foil as a cathode in the aqueous solution After washing and drying.

Examples of the composition and electrolysis conditions of the plating solution for chromium plating are shown below. In addition, the following conditions are preferred examples, and the type and amount of additives, and electrolysis conditions can be appropriately changed and adjusted as needed within a range that does not affect the effects of the present invention.

(Conditions for chrome plating)

Chromic anhydride (CrO ₃ )‥ converted to chromium (atoms), preferably 0.5 to 1.5 g/L, more preferably 0.8 to 1.1 g/L

Current density...preferably 0.3 to 0.6 A/dm ² , more preferably 0.4 to 0.6 A/dm ²

Electrolysis time...preferably 1 to 80 seconds, more preferably 1 to 60 seconds

Liquid pH...preferably 2.2 to 2.8, more preferably 2.3 to 2.6

Liquid temperature...preferably 15 to 50°C, more preferably 20 to 40°C

The benzotriazole treatment is performed by the following method: dissolving benzotriazole or a benzotriazole derivative in an organic solvent or water, immersing copper foil in the solution, and drying.

In addition, the silane coupling agent treatment is performed by the following method: dissolving the silane coupling agent in an organic solvent or water, immersing copper foil in the solution or coating the solution on the copper foil and then drying. Examples of the silane coupling agent used here include vinyl silane, epoxy silane, styrene silane, methacrylic silane, acrylic silane, amino silane, urea silane, mercapto silane, sulfide silane, isocyanate silane, and the like.

Furthermore, the above-mentioned chromate treatment, benzotriazole treatment, and silane coupling agent treatment can be appropriately combined.

The embodiment of the present invention has been described above, but the above-mentioned embodiment is only an example of the present invention. The present invention includes the concept of the present invention and all the modes included in the scope of the patent application, and various modifications can be made within the scope of the present invention. For example, the manufacturing method of electrolytic copper foil was demonstrated in detail in the above, but the method of manufacturing the copper foil of this invention is not limited to the said method. That is, as long as the characteristics of the bonding surface of the copper foil are controlled within the correct range of the present invention, it may be rolled copper foil (or surface-treated rolled copper foil), or may be copper foil produced by other manufacturing methods.

Example

Hereinafter, the present invention will be described in further detail based on examples, and the following is an example of the present invention.

(Examples 1 to 24 and Comparative Examples 1 to 20)

[1] foil making

First, the electrolytic copper foil was made into a foil with the composition of the electrolyte solution shown in Table 1 and the electrolysis conditions. At this time, the foil thicknesses of Examples 1 to 21 and Comparative Examples 19 and 20 were adjusted in advance to make the foil so that the thickness of the copper foil was 18 μm after the leveling treatment performed below. In addition, since the homogenization treatment was not performed on Comparative Examples 1 to 18, the foil was made at this time so that the thickness of the foil was 18 μm. In addition, Example 24 used the following rolled copper foil as the copper foil. The rolled copper foil was composed of oxygen-free rolled copper A, with a thickness of 17.8 μm and a surface roughness of 0.7 μm of the surface roughness Rz specified in JIS-B-0601. In addition, the elongation rate when the tensile test was performed at a temperature of 25 degrees was 6.0%.

In addition, in Table 1, "Cu" means copper sulfate pentahydrate converted into copper atoms, "MPS" means sodium 3-mercapto-1-propanesulfonate, "HEC" means hydroxyethyl cellulose, "PBF" Means low molecular weight glue, "ammonia" means ammonia with a concentration of 30% by mass, "Cl" means chlorine added as sodium chloride, "SPS" means sodium 4-styrene sulfonate, and "DDAC" means diallyl two Methylammonium chloride polymer (the same in Table 2 and Table 3 below).

[2] Homogenization

In Examples 1 to 21 and Comparative Examples 19 and 20, the electrolytic copper foil after the above [1] and the rolled copper foil of Example 24 were further homogenized according to the composition and electrolysis conditions of the electrolyte shown in Table 2. , Form a homogenization layer. The thickness of the copper foil after forming the leveling layer was 18 μm.

[3] Formation of roughened layer (roughened particle layer)

. Roughening plating treatment (1)

The copper foil obtained in the above [1] and [2] was used as a substrate, and the roughened surface was subjected to a roughening plating treatment. At this time, the composition of the plating solution and the electrolysis conditions are the conditions shown in Table 3. In addition, in Example 21 and Comparative Example 13, the roughening plating treatment (1) was not performed.

In addition, in Table 3, "Mo" represents ammonium molybdate converted to molybdenum atoms, "Co" represents cobalt sulfate heptahydrate converted to cobalt atoms, and "Fe" represents heptahydrate converted to iron atoms. Ferrous sulfate.

. Roughening plating treatment (2)

Then, the surface (rough surface) of the copper foil base body after the roughening plating treatment (1) is further subjected to a roughening plating treatment (2). At this time, the composition and electrolysis conditions of the plating solution are as follows. In addition, in Example 21 and Comparative Example 13, the roughening plating treatment (1) was not performed.

<Roughening plating (2) conditions>

Copper sulfate pentahydrate......‥Converted to copper (atom), 65.0g/L

sulfuric acid…………. 108g/L

Liquid temperature…………. 56°C

Current density………‥4A/dm ²

Electrolysis time…………‥1-20 seconds

[4] Formation of nickel-containing ground layer (nickel surface treatment layer)

Next, a ground layer as a base of the heat-resistant treatment layer is formed by electrolytic plating on the above-mentioned roughened layer. At this time, the nickel plating conditions are as follows. In addition, in Example 12 and Example 20, nickel treatment was not performed.

<Nickel plating conditions>

Nickel sulphate…………Converted to nickel (atom), 5.0g/L

Ammonium persulfate……40.0g/L

Boric acid…………28.5g/L

Liquid temperature…………. 28.5°C

Liquid pH…………3.8

Current density………‥1.5A/dm ²

Electrolysis time…………‥1-20 seconds

[5] Formation of zinc-containing heat-resistant treatment layer (zinc surface treatment layer)

Then, a heat-resistant treatment layer (amount of zinc adhesion: 0.05 mg/dm ² ) was formed on the ground layer by electrolytic plating. At this time, the galvanizing conditions are as follows. In addition, Example 20 was not subjected to zinc treatment.

<Galvanizing conditions>

Zinc Sulfate Heptahydrate.... Converted to zinc (atom), 10g/L

Sodium hydroxide.... 50g/L

Liquid temperature…………. 32°C

Current density………‥5.0A/dm ²

Electrolysis time…………‥1-20 seconds

[6] Formation of chromium-containing antirust treatment layer (chromium surface treatment layer)

Furthermore, an anti-corrosion treatment layer is formed by electrolytic plating on the heat-resistant treatment layer. At this time, the chrome plating conditions are as follows. In addition, in Examples 16 and 20, chromium treatment was not performed.

<Chrome plating conditions>

Chromic anhydride (CrO ₃ ).... Converted to chromium (atoms), 0.9g/L

Liquid temperature…………. 32.0°C

Liquid pH…………2.5

Current density………‥0.5A/dm ²

Electrolysis time…………‥1-20 seconds

[7] Formation of silane coupling agent layer

Finally, an aqueous solution of 3-methacryloxypropyltrimethoxysilane with a concentration of 0.7% by mass was coated on the anti-rust treatment layer and dried to form a silane coupling agent layer (the adhesion amount of silane is converted to silicon atoms, 0.0070 mg/dm ² ).

(Evaluate)

The copper foils described in the above examples and comparative examples were subjected to the following measurements and evaluations. Each evaluation condition is as follows. The results are shown in Table 4.

In addition, in the following measurement, the adhesion surface of the copper foil is the surface of the silane coupling agent layer which is the outermost layer of the copper foil (the surface of the outermost layer on the rough surface side of the electrolytic copper foil as a base). In Table 4, the surface treatment layer (i) consists of a roughened particle layer, a nickel surface treatment layer, a zinc surface treatment layer, a chromium surface treatment layer and a silane coupling agent layer, and the surface treatment layer (ii) consists of a nickel surface treatment layer, zinc Surface treatment layer, chromium surface treatment layer and silane coupling agent layer. Surface treatment layer (iii) is composed of roughened particle layer, zinc surface treatment layer, chromium surface treatment layer and silane coupling agent layer. Surface treatment layer (iv) consists of The roughened particle layer, the nickel surface treatment layer, the zinc surface treatment layer and the silane coupling agent layer are composed, and the surface treatment layer (v) is composed of the roughened particle layer and the silane coupling agent layer.

[1] Number of fluctuations Wn

For the bonding surface of the copper foil, the average length of the roughness pattern AR (mm) was measured in accordance with JIS B 0631: 2000. The measurement was performed at five arbitrary locations of each copper foil, and the average value (N=5) was used as the average length AR of the roughness pattern of each copper foil. In addition, the measuring device uses a surface roughness measuring machine (Surfcorder SE3500, manufactured by Kosaka Laboratory Co., Ltd.), and the measuring conditions are A=0.1mm, B=0.5mm, In=3.2mm, λs=2.5μm, and the measuring range is in the TD direction. (The vertical direction with respect to the longitudinal direction of the copper foil (corresponding to the film forming direction)) is a range of 50 mm in length. From the measured average length AR of the roughness pattern, the average number of undulations (1/AR) on the 1 mm line is calculated as the number of undulations Wn (number/mm).

[2] Average depth of roughness graph R

On the bonding surface of the copper foil, the average depth R (μm) of the roughness pattern was measured in accordance with JIS B 0631:2000. The measurement was performed at five arbitrary locations of each copper foil, and the average value (N=5) was used as the average depth R of the roughness pattern of each copper foil. In addition, the measuring device uses a surface roughness measuring machine (Surfcorder SE3500, manufactured by Kosaka Laboratory Co., Ltd.), and the measuring conditions are A=0.1mm, B=0.5mm, In=3.2mm, λs=2.5μm, and the measuring range is in the TD direction. (The vertical direction with respect to the longitudinal direction of the copper foil (corresponding to the film forming direction)) is a range of 50 mm in length.

[3] Contact roughness Rz, Ra

The ten-point average roughness Rz (μM) and the arithmetic average roughness Ra (μM) of the bonding surface of the copper foil were measured in accordance with JIS B 0601:1994. The measurement was performed at five arbitrary locations of each copper foil, and the average value (n=5) was used as the ten-point average roughness Rz and the arithmetic average roughness Ra of each copper foil, respectively. In addition, as the measuring device, a contact surface roughness measuring machine (SE1700, manufactured by Kosaka Laboratory Co., Ltd.) was used. The measurement conditions are a measurement length of 4.8 mm, a sampling length of 4.8 mm, and a cut value of 0.8 mm.

[4] Non-contact roughness Rz, Ra

Except that a non-contact laser microscope (VK8500, manufactured by Keynes Co., Ltd.) was used as a measuring device, the ten-point average roughness Rz (μm) and Arithmetic average roughness Ra (μm).

[5] Surface area ratio A/B

On the bonding surface of the copper foil, a laser microscope (VK8500, manufactured by Keynes Co., Ltd.) was used to measure the three-dimensional surface area (μm ² ). The measurement was performed at five arbitrary locations of each copper foil, and the average value (N=5) was used as the three-dimensional surface area of each copper foil. In addition, the measurement field of view was a range of 30.0 μm×44.9 μm, and this was regarded as the two-dimensional surface area corresponding to the three-dimensional surface area. The surface area ratio (three-dimensional surface area A/two-dimensional surface area B) is calculated from the measured three-dimensional surface area A and the corresponding two-dimensional surface area B.

[6] Adhesion amount of nickel, zinc, chromium and silane

Measure the adhesion amount of nickel, zinc, chromium and silane. A fluorescent X-ray analyzer (ZSX Primus, manufactured by Rigaku Co., Ltd.) was used for the measurement, and the analysis was performed with an analysis diameter of Φ35 mm. In addition, the adhesion amount of zinc and silane is as described above.

[7] Transmission loss

A resin substrate was bonded to the bonding surface of the copper foil to produce a sample of a substrate for measuring transmission characteristics. The resin substrate uses a commercially available polyphenylene ether resin (ultra-low transmission loss multilayer substrate material MEGTRON6, manufactured by Panasonic Corporation), the curing temperature during bonding is 210°C, and the curing time is 2 hours. The structure of the substrate for transmission loss measurement adopts a microstrip line structure, which is adjusted to a conductor length of 400mm, a conductor thickness of 18μm, a conductor width of 0.14mm, an overall thickness of 0.31mm, and a characteristic impedance of 50Ω. For the measurement sample adjusted as described above, the vector network analyzer E8363B (KEYSIGHT TECHNOLOGIES) was used to measure the transmission loss at 10 GHz and 40 GHz. In addition, the evaluation result uses dB/m as the unit, and shows a value obtained by converting the transmission loss measured with a conductor length of 400 mm into a transmission loss value with a conductor length of 1000 mm (the value of the transmission loss measured with a conductor length of 400 mm multiplied by 2.5). In this embodiment, the transmission loss of 19.5 dB/m or less at 10 GHz is set as the passing level, and the transmission loss of 66.0 dB/m or less at 40 GHz is set as the passing level.

[8] Reflow heat resistance

FIG. 2 shows a schematic diagram of the manufacturing procedure of the test piece T2 of the reflow heat resistance test. First, as shown in Figure 2(a), prepare a commercially available polyphenylene ether resin (ultra-low transmission loss multilayer substrate material MEGTRON6, manufactured by Panasonic Corporation) as the first resin substrate B1, and laminate and bond on both sides of B1 Each copper foil M1 described in the present embodiment or the comparative example produces a copper-clad laminate P. Next, as shown in FIG. 2(b), the copper-clad laminate P is etched with a copper chloride solution to dissolve all the copper foil portions M1. Thereafter, by laminating and bonding the second resin substrate B2 on both sides of the etched first resin substrate (resin core layer) B1 (Figure 2(c)), the second resin substrate (pre- The dipping material layer) B2 was laminated and bonded to each of the copper foils M2 described in the present example or the comparative example to produce a test piece T2 (100mm×100mm) for measuring the reflow heat resistance (FIG. 2(d)). Five test pieces were made for each copper foil. Next, pass the manufactured test piece T2 through a reflow oven with a maximum temperature of 260°C and a heating time of 10 seconds, and visually observe whether the copper foil and resin (M2-B2) or resin and resin (B2-B1) are on each layer. Swelling (peeling between layers) occurs. After that, the test piece T2 where interlayer peeling was observed on both the copper foil and the resin and the resin and the resin was removed, and the other test pieces T2 were passed through the reflow furnace under the above heating conditions again, and the reflow furnace was repeatedly passed through the reflow furnace to observe the interlayer Peeling was performed until swelling was observed between the layers of both the copper foil and the resin and the resin and the resin. In addition, the number of passes through the reflow furnace when interlayer peeling occurred was measured between the copper foil and the resin and between the resin and the resin layers. In this measurement, 5 test pieces were applied to each copper foil, and the average value (N=5) of the number of passes of each reflow furnace was evaluated as the reflow heat resistance of each copper foil. Here, the reflow heat resistance between the copper foil and the resin means the heat resistance of the joint between the copper foil and the prepreg layer, and the reflow heat resistance between the resin and the resin means the joint between the core layer and the prepreg layer For the heat resistance, the more passes through the reflow furnace, the better the heat resistance of the two. In this embodiment, the number of passes through the reflow furnace until the interlayer peeling is observed for 8 or more times of the copper foil and the resin and between the resin and the resin layers is regarded as an acceptable level.

[9] Adhesion strength (peel strength)

The resin substrate was bonded to the bonding surface of the copper foil to produce a sample for measurement. The resin substrate uses a commercially available polyphenylene ether resin (ultra-low transmission loss multilayer substrate material MEGTRON6, manufactured by Panasonic Corporation), the curing temperature during bonding is 210°C, and the curing time is 1 hour. The prepared measurement sample was etched into circuit wiring with a width of 10 mm, the resin side was fixed to a stainless steel plate with double-sided tape, the circuit wiring was peeled in a 90-degree direction at a speed of 50 mm/min, and the peel strength (kN/ m) As an index of adhesion strength. The measurement was performed using a universal material testing machine (Tensilon, manufactured by A&D Co., Ltd.). In this example, the peel strength (initial adhesiveness) of 0.4 kN/m or more was set as the pass level.

As shown in Table 4, it can be confirmed that the number of undulations Wn on the bonding surface of the copper foil with the resin substrate of the examples 1 to 24 is controlled at 11 to 30 per mm, and the average depth R of the roughness pattern is controlled by Controlled at 0.20 to 1.10 μm, the copper foil has low transmission loss, excellent reflow heat resistance, and can exhibit high adhesion strength.

In contrast, it can be confirmed that the number of undulations Wn of the copper foils of Comparative Examples 1 to 20 on the bonding surface with the resin substrate is not controlled at 11 to 30/mm, or the average depth R of the roughness pattern is not It is controlled to 0.20 to 1.10 μm, or both are not controlled. Therefore, compared with the copper foil described in Examples 1 to 24, any one or more of transmission loss, reflow heat resistance, and adhesion strength is inferior.

Claims (13)

A copper foil characterized in that the roughness pattern is determined by the pattern method specified in JIS B0631:2000, and when the number of undulations Wn and the average depth R of the roughness pattern calculated from the roughness pattern are used to express the characteristics of the bonding surface of the copper foil, The number of undulations Wn is 11 to 30/mm, and the average depth R of the roughness pattern is 0.20 to 1.10 μm. According to the copper foil described in item 1 of the scope of patent application, the number of undulations Wn is 12 to 27 per mm, and the average depth R of the roughness pattern is 0.30 to 0.90 μm. According to the copper foil described in item 2 of the scope of patent application, wherein the number of undulations Wn is 14 to 22/mm, and the average depth R of the roughness pattern is 0.40 to 0.80 μm. The copper foil according to any one of items 1 to 3 in the scope of the patent application, wherein the surface area ratio of the measured three-dimensional surface area of the bonding surface to the two-dimensional surface area when measured on a plane is 1.05 to 2.85. The copper foil according to item 4 of the scope of patent application, wherein the surface area ratio of the measured three-dimensional surface area of the bonding surface to the two-dimensional surface area when measured on a plane is 2.00 to 2.70. The copper foil according to any one of items 1 to 3 in the scope of the patent application, wherein the copper foil is an electrolytic copper foil. The copper foil according to any one of items 1 to 3 in the scope of the patent application, wherein the bonding surface is a rough surface. The copper foil according to any one of items 1 to 3 in the scope of the patent application, wherein the copper foil is provided with a copper foil base and the copper foil base on the bonding surface side A surface-treated copper foil with a surface treatment layer on the surface of the body, the surface treatment layer contains at least one layer of a roughened particle layer, a nickel surface treatment layer, a zinc surface treatment layer, a chromium surface treatment layer, and a silane coupling agent layer, and the bonding The surface is the outermost surface of the surface treatment layer. The copper foil described in item 8 of the scope of patent application, wherein the surface treatment layer contains the nickel surface treatment layer, and the adhesion amount of nickel is 0.010 to 0.800 mg/dm ² . The copper foil described in item 9 of the scope of patent application, wherein the adhesion amount of the nickel is 0.020 to 0.400 mg/dm ² . The copper foil according to item 8 of the scope of patent application, wherein the surface treatment layer contains the chromium surface treatment layer, and the adhesion amount of chromium is 0.010 to 0.300 mg/dm ² . The copper foil described in item 11 of the scope of patent application, wherein the adhesion amount of the chromium is 0.015 to 0.200 mg/dm ² . A copper clad laminated board has the copper foil described in any one of items 1 to 12 in the scope of the patent application, and an insulating substrate adhesively laminated on the adhesive surface.

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