CN1352805A - Substrate with at least two metallized polymer bumps for soldered connection to wiring - Google Patents

Abstract

A substrate (S) with at least two metallized polymer bumps (PS), especially a polymer stud grid array, is configured in such a way that the polymer bumps (PS) have at least one step (ST) and at least one elevation (E). The geometry of the solder bumps (PS) ensures that the soldered connections to the wiring (V) are secure and guarantees reproducible layer thickness for the solder (L).

Description

Substrate with at least two metallized polymer protrusions for soldering to a wiring

Integrated switching circuits always have a high number of wiring points and are increasingly miniaturized. Difficulties in solder paste application and tooling are expected to arise with increasing miniaturization, which should be eliminated by new housing shapes, here especially in ball grid array assemblies for single, small or multiple The micromodule of a chip is very prominent (DE-Z May 1994, pp. 54, 55). These modules are based on a body-contacted substrate on which the chips are contacted, for example by contact wires or using the flip-chip method. On the lower surface of this substrate is a ball grid array (BGA), which is also often referred to as a solder grid array or a solder bump grid. The ball grid lattice includes solder bumps arranged on the lower surface of the substrate, which enable a surface mount on a printed circuit board or on a modular assembly. Through this layout of the solder bumps, a higher number of connection points can be achieved in a coarse grid, such as 1.27mm.

In the so-called MID technology (MID=Moulded Interconnection Devices) die-cast parts with integrated conductor sets are used instead of conventional printed circuits. Advanced thermoplastics suitable for die-casting of three-dimensional substrates are the basis of this technology. This thermoplastic is distinguished by better mechanical, chemical, electrical, and environmental-technical properties than conventional substrate materials for printed circuits. In a special direction of MID technology, the so-called SIL technology (SIL=Spritzgiepteile mit integrierten Leiterziigen, i.e. die casting with integrated conductor set), the usual mask technology is abandoned by using a special laser structured decomposition process , to obtain a metal layer structure on the die casting. Further mechanical and electrical functions can thus be integrated in the three-dimensional die-cast part with structured metal coating. The housing bracket has both a guiding function and a switch connection function, while the metallization layer, in addition to its wiring and connection functions, also serves as electromagnetic shielding and guarantees a good thermal drift. In order to produce an electrically conductive transverse connection of the two wiring devices on the surface of the die-cast part, corresponding through-body contact holes are already produced during die-casting. During the metal spraying of the die casting, the inner wall of the whole body contact hole is also covered by the metal layer. Other details of the production of three-dimensional die-cast parts with an integrated lead set can be found, for example, in DE-A-37 32 249 or EP-A-0 361 192.

It can be seen that WO-A-89/00346 shows a single-chip module, a three-dimensional die-cast base made of an electrically insulating polymer on the bottom surface of the base is co-formed with protrusions during die-casting, and these protrusions are also floor plan. On the upper side of this substrate, an integrated circuit chip (IC chip) is arranged, and its connection points are connected together with rails formed on the surface of the substrate through fine wiring harnesses. The rails themselves are connected via through-body contacts to external terminal points formed on the protrusions.

It can be seen that WO-A-96 096 46 shows a so-called Polymer Columnar Grid Array (PSGA) which combines the advantages of Ball Grid Array (BGA) with the advantages of MID technology. This new structural form, called Polymer Column Grid Array (PSGA), is based on Ball Grid Array (BGA), where the concept of "Polymer Column" should refer to co-formation during die-casting of the substrate. polymer protrusions. Suitable configurations for this new single, small or multiple chip module include

- a three-dimensional base die-cast from an electrically insulating polymer;

- polymeric protrusions arranged planarly on the bottom surface of the substrate and co-formed during the die-casting process;

- External terminal points via a detachable terminal surface on polymer protrusions

- a conductor set formed at least on the bottom surface of the substrate, which connects the external connection points with the internal connection points.

- at least one chip arranged on a substrate, the connection points of which are electrically conductively connected to the internal connection points.

During die-casting of this substrate, the manufacture of the polymer protrusions is simple and cost-effective. In addition, it is also possible, preferably with minimal effort, to produce the external connection points on the polymer protrusions, while at the same time producing the wire groups using MID technology or SIL technology. By utilizing the laser-finest structuring preferred by SIL technology, a high number of external connection points can be achieved on top of the polymer protrusions in a fine grid.

It should also be emphasized that the increase in temperature of the polymer protrusions corresponds to an increase in the temperature of the circuit housing the module and the temperature of the substrate. A high degree of reliability of the soldering can thus be achieved in the case of frequent temperature changes.

It can also be seen from US-A-5 477 087 that the elastic properties and temperature properties of the polymer protrusions can be fully utilized when connecting with electronic components, such as semiconductors. To do this, a barrier metal layer is first created on the aluminum electrodes of the electronic component, on which the polymer protrusions are formed. The formed polymer protrusion is then covered with a layer of metal, which has a lower melting point.

If the connection between a polymer columnar grid lattice or other metallized electrical component and a wiring such as a printed circuit board is achieved by reflow soldering, there is a danger that the melted flux will The protruding metallized coating is drawn upwards. But this phenomenon, which occurs at about 75% of the polymer protrusions, itself leads to an unreproducible solder layer thickness under the polymer protrusions, which may even short-circuit adjacent conductor lines.

The problem to be solved by the invention set forth in claim 1 is to ensure a reproducible solder layer thickness below the polymer protrusions in a substrate with polymer protrusions for soldering to wiring.

The invention is based on the knowledge that, by means of the geometry of the polymer protrusion with at least one bulge, the shoulder or the shoulders formed thereby prevent the jumping of molten solder. Reproducible solder layer thicknesses can thus be produced under the polymer bumps which themselves ensure a highly reliable soldering. This can also eliminate the risk of short circuits due to jumping flux.

Preferred developments of the invention are given in the dependent claims.

The refinement according to claim 2 is particularly suitable for the production of substrates with integrated polymer protrusions by die casting. The dimensions of the cylindrical elevations of the polymeric columnar grid array specified in claim 3 render the welding particularly reliable.

In the variants specified in claims 4, 5 and 6, for the geometry of the polymer protrusions, those solder jumps are also prevented by shoulders. Thus, the possibility exists that the geometry of the polymeric protrusions can be tuned to suit a specific application form.

Embodiments of the invention are shown in the drawings and described further below.

Figure 1 shows a sectional view of a substrate with integrally formed stepped polymeric protrusions.

FIG. 2 shows a polymeric protrusion of the substrate shown in FIG. 1 with a metal coating and a set of wires extending from the polymeric protrusion.

Figure 3 shows the soldering between the polymer bumps shown in Figure 2 and the wires.

Figure 4 shows a first variant with double-layer stepped polymer protrusions.

Shown in FIG. 5 is a second variant of polymer protrusions with protrusions arranged on a shoulder.

Figure 6 shows a third variant of the polymeric protrusion with an annular ridge.

Figure 1 shows a cross-sectional view of a substrate S on which co-formed polymer protrusions PS, or polymer columns, are arranged on its bottom surface U in order to form a polymer columnar grid array during die casting. . It can be seen that the polymer projection PS of simple conical configuration is provided with a cylindrical elevation E at its bottom end. The diameter of the cylindrical elevation E is dimensioned in such a way that an annular shoulder ST transitions into the further polymer projection PS. In the exemplary embodiment described, it is shown that a polymer protrusion PS has a diameter D of 400 μm in the region of its base and a height H as the distance between the bottom surface U of the substrate S and the shoulder ST of 400 μm. The diameter d of the cylindrical ridge E was 160 μm, and the height h of the cylindrical ridge E was 50 μm.

FIG. 2 shows a polymer protrusion PS obtained by laser finest structuring of a metal layer obtained by the protrusion shown in FIG. 1 over the entire plane of the substrate S. FIG. It can be seen that the polymeric protrusion PS including the cylindrical elevation E is provided with a metal coating M, from which the polymeric protrusion PS on the bottom surface U of the substrate S leads a lead group LZ.

FIG. 3 shows the soldering between the polymer protrusion PS shown in FIG. 2 and a wiring V, which in the shown embodiment is configured as a printed circuit board LP with connection gaskets arranged on the surface. become. It can be clearly seen that during reflow soldering, the entire flux L stays in the area between the shoulder ST and the connection gasket AP; it does not jump up to the wire group on the side as in the polymer protrusion without the stepped structure LZ office. A reproducible layer thickness of the solder L is ensured by the geometry of the stepped polymer protrusions PS.

The first variant shown in FIG. 4 is a polymeric protrusion called PS, which is integrally formed on a substrate S1. An annular elevation E1 and a cylindrical elevation E10 are formed by a two-level step of the polymer protrusion PS1. The corresponding annular shoulders are referred to as ST1 or ST10.

The second variant shown in Figure 5 is a polymeric protrusion called PS2, which is integrally formed on a substrate S2. A total of four spaced apart cylindrical elevations E2 are arranged on a shoulder ST2 configured as a platform.

A third variant shown in FIG. 6 is a polymeric protrusion called PS3, which is integrally formed on a substrate S3. Here an annular elevation E3 rests on a shoulder ST3 which is likewise designed as a platform.

In addition to the simple polymer protrusions with frustoconical shape shown in FIGS. 1 to 6 , other cross-sectional forms of polymer protrusions or elevations can also be used. Here, however, the configuration of at least one shoulder which prevents a lateral jump of the flux during reflow soldering plays a decisive role.

Claims (6)

1. be used for substrate (S with wiring (V) welding; S1; S2; S3), the polymer bumps (PS that has at least two metal sprayings; PS1, PS2; PS3) with at substrate (S; S1; S2; S3) lower surface (U) is gone up by polymer bumps (PS; PS1; PS2; PS3; ) guiding lead group (LZ), wherein, these polymer bumps (PS; PS1; PS2; PS3) have at least one and be used to construct at least one protuberance (E; E1; E10; E2; E3) shoulder (ST; ST1, ST10; ST2; ST3).

2. according to the described substrate of claim (S), it is characterized in that the cylindrical protuberance (E) with polymer bumps (PS) arranged concentric.

3. substrate according to claim 2 (S) is characterized in that, the diameter (d) of cylindrical protuberance (E) at 100 μ m between the 300 μ m, its height (h) at 25 μ m between the 250 μ m.

4. substrate according to claim 1 (S1) is characterized in that, polymer bumps (PS1) is provided with two protuberance (E1; E10) and two shoulder (ST1; ST10).

5. substrate according to claim 1 (S2) is characterized in that, polymer bumps (PS2) is provided with the protuberance a plurality of at regular intervals (E2) that is arranged on the shoulder (ST2).

6. substrate according to claim 1 (S3) is characterized in that, polymer bumps (PS3) is provided with the ring uplift (E3) that is arranged on the shoulder (ST3).

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