WO2001082372A1

WO2001082372A1 - Polymer stud grid array having feedthroughs and method for producing a substrate for a polymer stud grid array of this type

Info

Publication number: WO2001082372A1
Application number: PCT/DE2001/000679
Authority: WO
Inventors: Karl-Heinz Keilholz; Lothar Müller; Dirk Striebel; Richard Thelen; Jozef Van Puymbroeck
Original assignee: Siemens Aktiengesellschaft
Priority date: 2000-04-20
Filing date: 2001-02-21
Publication date: 2001-11-01
Also published as: TW502407B

Abstract

The invention relates to a polymer stud grid array having feedthroughs and to a method for producing a substrate for a polymer stud grid array of this type. During injection molding or hot stamping of the substrate (S) for a polymer stud grid array, polymer protuberances (PS) are formed on the underside (U) and recesses (V1) are formed on the top side (O) or on the underside (U). Through holes (DL1) are placed in the bottoms (B1) of the recesses (V1), especially by means of laser boring, in order to form feedthrough holes. The feedthrough holes are produced quickly and with little effort.

Description

description

Polymer stud grid array with vias and method for producing a substrate for such a polymer stud grid array

Integrated circuits are getting more and more connections and are being miniaturized more and more. The difficulties with solder paste application and assembly expected from this increasing miniaturization are to be remedied by new housing shapes, in particular single, few or multi-chip modules in the ball grid array package to be emphasized here (DE-Z productronic 5, 1994, Pages 54, 55). These modules are based on a plated-through substrate on which the chips are contacted, for example, via contact wires or by means of flip chip assembly. On the underside of the substrate is the Ball Grid Array (BGA), which is often referred to as a Solder Grid Array or a Solder Bump Array. The ball grid array comprises solder bumps arranged flat on the underside of the substrate, which enable surface mounting on the printed circuit boards or assemblies. Due to the flat arrangement of the solder bumps, large numbers of connections can be realized in a coarse grid of, for example, 1.27 mm.

So-called MID technology (MID = Molded Interconnection Devices) uses injection molded parts with integrated conductor tracks instead of conventional printed circuits. High-quality thermoplastics, which are suitable for injection molding three-dimensional substrates, form the basis of this technology. Thermoplastics of this type are distinguished from conventional substrate materials for printed circuits by better mechanical, chemical, electrical and environmental properties. In a preferred direction of MID technology, the structuring of a metal layer applied to the injection molded parts is carried out by dispensing with the mask technology which is otherwise customary by means of a special layer. ω ω N3 IV) P ¹ P ¹ c_π o Cn o U1 o Cn

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new design suitable for single, Few or multi-chip modules

an injection-molded, three-dimensional substrate made of an electrically insulating polymer, polymer bumps arranged flat on the underside of the substrate and molded during injection molding,

- external connections formed on the polymer bumps by a detachable end surface,

- Conductor tracks formed at least on the underside of the substrate, which connect the external connections to internal connections, and

- At least one chip arranged on the substrate, the connections of which are electrically conductively connected to the internal connections.

In addition to the simple and cost-effective production of the polymer bumps during the injection molding of the substrate, the production of the external connections on the polymer bumps can also be carried out with minimal effort together with the production of the conductor tracks, which is common in MID technology. Due to the preferred fine laser structuring, the external connections on the polymer bumps with high numbers of connections can be realized in a fine grid. It should also be emphasized that the temperature expansion of the polymer bumps corresponds to the temperature expansion of the substrate and the wiring that receives the module. As a result, high reliability of the soldered connection is achieved even with frequent temperature fluctuations.

In German patent application 100 37 292.9-33, a method for producing a substrate for a polymer stud grid array by hot stamping was proposed as an alternative to injection molding. In this method, a raw body, preferably a film, is heated, whereupon bumps and / or depressions are produced on at least one surface by means of a stamp. As a material for the substrates ω cυ D fυ P ¹ I- ¹ cn o tπ o Cn o Cn

denähte. On the other hand, the depth of the through holes is considerably reduced by the depth of the depressions, so that the introduction of through holes into the bottom of the depressions takes only a very short time. Another advantage is that the recesses create clean and burr-free edges on the corresponding surface of the substrate. Finally, the through holes, which are graduated in their geometry, enable simple sealing by means of solder mask or the like, so that with the so-called transfer gold, i.e. when encapsulating a chip applied to the substrate, the material used for the encapsulation cannot flow to the opposite side of the substrate.

The two-stage production of through-holes with depressions formed during the hot stamping of the substrate and subsequently through holes made in the bottom of the wells also offers a number of advantages, of which the rapid production of the through-holes and the simple sealing of the stepped through-holes are particularly noteworthy.

Advantageous refinements of the polymer stud grid array according to the invention emerge from claims 2 to 7.

Advantageous refinements of the method according to the invention for producing a substrate for a polymer stud grid array are specified in claims 9 to 16.

The embodiment according to claims 2 or 9 favors the removal of the substrate produced by injection molding or by hot stamping from the injection mold.

The embodiment according to claims 4 or 10 enables particularly clean edges of the via holes on the top of the substrate. The configuration according to claims 5 or 11 enables particularly clean edges of the via holes on the underside of the substrate.

The development according to claim 6 or 13 enables a particularly rapid introduction of the through holes into the bottom of the depressions, this time for the introduction of the through holes being able to be shortened even further by the development according to claim 7 or 14.

The embodiment according to claim 12 enables the production of two or more vias in the area of a single recess.

According to claim 15, the through holes are preferably made by drilling in the bottom of the wells. According to claim 16, the through holes can be made very quickly in the bottom of the depressions by laser drilling with little effort.

Embodiments of the invention are shown in the drawing and are described in more detail below. 1 shows a section through a substrate for a polymer stud grid array after the injection molding process,

2 shows the detail II according to FIG. 1, FIG. 3 shows a section corresponding to FIG

Making through holes, FIG. 4 shows a section according to FIG. 3 after the application and structuring of a metallization,

Figure 5 shows the section of Figure 4 after sealing the

Via holes, FIG. 6 shows a section through a second embodiment of a substrate for a polymer stud grid array after the injection molding process,

FIG. 7 shows a section corresponding to FIG. 6 after through holes have been made, FIG. 8 shows a section through a third embodiment of a substrate for a polymer stud grid array with four through holes per depression,

Figure 9 is a plan view of the recess and the through holes of the substrate shown in Figure 8 and

Figure 10 shows the geometry of the via holes of the substrate shown in Figure 3.

FIG. 1 shows a section through a substrate S for a polymer stud grid array, the substrate S being provided on its underside U with a multiplicity of integrally molded "polymer studs" or polymer bumps PS. The polymer bumps PS, which are stepped on their underside, are also formed during the injection molding of the substrate S, as are the funnel-shaped depressions VI which are introduced into the upper side 0 of the substrate S. The funnel-shaped depressions VI are located at those points on the substrate S at which plated-through holes later are to form electrically conductive connections between the top 0 and bottom U of the substrate S. High-temperature resistant thermoplastics such as polyetherimide or polyethersulfone are suitable as substrate material, however (LCP (Liquid Crystalline Polymers) is preferably used.

FIG. 2 shows the detail II of FIG. 1 with two funnel-shaped depressions VI made in the upper side of the substrate S. The bottom of each funnel-shaped depression VI is denoted by B1.

According to FIG. 3, through holes DL1 are introduced into the injection molded part shown in FIG. 2, which, together with the depressions VI, form via holes. The through holes DL1 made in the bottom B1 (see FIG. 2) are produced, for example, by mechanical drilling or by laser drilling, the hole being produced both from the top 0 to the bottom U and from the bottom cυ cυ f MP ¹ P ¹

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pour funnel-shaped depressions V2 in the underside U of the substrate S.

In the injection molded part designed according to FIG. 6, through holes DL2 are then introduced according to FIG. 7, which form via holes together with the depressions V2. The via holes DL2 made in the bottom B2 of the depressions V2 can also be produced here again by mechanical drilling or by laser drilling.

FIG. 9 shows a section through a third embodiment of a substrate S for a polymer stud grid array. A total of four through holes DL3 are made in the bottom B3 of a depression V3 formed during the injection molding of the substrate S, the distribution of which in the depression V3 can be seen from the top view shown in FIG. 9. FIG. 9 also shows that the depression V3 has a square shape here.

FIG. 10 shows the geometry of the through-holes of the substrate S shown in FIG. 3 in a highly simplified schematic representation. The conical depression VI has on the upper side 0 of the substrate S a diameter denoted by a, while the diameter in the region of the bottom B1 ( see FIG. 2) is denoted by b. The through hole DL1 made in the bottom B1 of the depression VI has a diameter denoted by d. The thickness of the substrate S without taking into account the height of the polymer bumps PS is denoted by s, while the depths of

Well VI and through hole DLl are designated t and c, respectively.

For a typical substrate S consisting of LCP with laser-drilled through holes DL1, the following dimensions can be specified, for example: a 0, 20 mm b 0, 14 mm d 0, 10 mm s 0, 35 mm t 0, 25 mm c 0, 10 mm

The exemplary embodiments of the invention described above can also be implemented in a corresponding manner in the manufacture of the substrates by hot stamping. Here, a raw body, preferably a film, is heated, whereupon the polymer bumps and the depressions are produced in one operation by means of an embossing stamp. Further details of the production of substrates for a polymer stud grid array by hot stamping are described in German patent application 100 37 292.9-33, the disclosure of which is part of the present patent application.

Claims

claims

1. Polymer Stud Grid Array with a substrate (S) made of an electrically insulating polymer produced by injection molding or by hot stamping, arranged flat on the underside (U) of the substrate (S) and molded during injection molding or hot stamping (PS) , - on the polymer bumps (PS) formed external connections (AA), on the underside of the substrate (S) formed conductive lines (LZU), which extend between the external connections (AA) and to the upper side of the substrate (S) leading through holes , wherein the via holes are formed by depressions (VI; V2; V3) formed during injection molding or hot stamping of the substrate (S) and through holes (DL1; DL1; DL2; DL3) are formed.

2. Polymer stud grid array according to claim 1, characterized in that the depressions (VI; V2; V3) are funnel-shaped.

3. Polymer stud grid array according to claim 1 or 2, characterized in that the depressions (VI) in the top (0) of the substrate (S) are introduced.

4. Polymer stud grid array according to claim 1 or 2, characterized in that the depressions (V2) are introduced into the underside of the substrate (S).

5. Polymer Stud Grid Array according to one of the preceding claims, characterized in that in the ground (B3) of the depressions (V3) at least two through holes (DL3) are introduced.

6. Polymer Stud Grid Array according to one of the preceding claims, characterized in that the depth (t) of the depressions (VI) is at least 50% of the thickness (s) of the substrate (S).

7. Polymer stud grid array according to one of the preceding claims, characterized in that the depth (t) of the depressions (VI) is approximately 70% to 80% of the thickness (s) of the substrate (S).

8. A method for producing a substrate (S) for a polymer stud grid array comprising the following steps:

Injection molding or hot stamping of the substrate (S) with integrally molded polymer bumps (PS) on the underside (U) and with depressions (VI; V2; V3) in the area of later via holes, - Making through holes (DLl; DL2; DL3) in the ground (B1; B2; B3) of the depressions (VI; V2; V3).

9. The method according to claim 8, characterized in that the depressions (VI; V2; V3) are funnel-shaped.

10. The method according to claim 8 or 9, characterized in that the depressions (VI) in the top (O) of the substrate (S) are introduced.

11. The method according to claim 8 or 9, characterized in that the depressions (V2) are introduced into the underside (U) of the substrate (S).

12. The method according to any one of claims 8 to 11, characterized in that in the bottom (B3) of the wells (V3) at least two through holes (DL3) are introduced.

13. The method according to any one of claims 8 to 12, characterized in that the depressions (VI) with a

Depth (t) can be introduced, which is at least 50% of the thickness (s) of the substrate (S).

14. The method according to any one of claims 8 to 13, characterized in that the depressions (VI) with a

Depth (t) can be introduced, which is about 70% to 80% of the thickness (s) of the substrate (S).

15. The method according to any one of claims 8 to 14, characterized in that the through holes (DLl; DL2;

DL3) are drilled.

16. The method according to any one of claims 8 to 15, characterized in that the through holes (DLl; DL2; DL3) are made by laser drilling.