Carrier plate for integrated circuit

(42) Date of commencement of the patent: 15. 3. 1996 (45) Date of issue: 25.11.1996 (56) Documentation:

EP 0448483A1 US 3871728A US 4828515A

Support plate for integrated circuits, with openings whose wall is metallically conductive, wherein contact nails (1) are provided, which protrude into the openings (6) and over the back of the support plate (7 ) protrude.

(73) Patent owner:

AB MICROELECTRONICS SOCIETY WITH LIMITED LIABILITY

A-5013 SALZBURG, SALZBURG (AT).

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AT 401 704 db Krams

AT 401 704 Β

The invention relates to a support plate for integrated circuits, with openings whose wall is metallically conductive, wherein in the openings contact bodies are provided which protrude beyond the back of the support plate and project into a solder paste, which on the front of a parallel to the support plate base plate (Motherboard) is printed.

Such carrier plates are often constructed in multiple layers, wherein the internal functional levels are related through the plated-through openings with the outside world. Depending on the material from which the carrier plates are made, different contact bodies are used to derive signals from the openings on the rear side of the carrier plate.

Conventional contact bodies consist of solder balls, which are melted butt on the back of the support plate. In the case of ceramic support plates, the melting point of these solder balls may be relatively high, whereas in the case of organic support plates, a soft solder must be used which often loses its shape when connected to the base plate printed with solder paste. In the case of lack of uniformity of the solder balls, it may also happen that individual contacts to the base plate fail.

The invention provides that the contact bodies are pressed into the apertures contact nails whose heads protrude beyond the back of the support plate.

Such nails can be easily made of a material for which the temperature used in the connection of carrier plate and motherboard is unproblematic and which also tolerates a heat shock occurring for other reasons. The contact between the nails and the walls of the openings is much better defined than in the case of solder. This is especially true when the contact pins have a square cross-section shaft, the edges of which engage in the wall of the openings and thereby produce a gas-tight connection to this wall. The contact bodies according to the invention can be produced very simply because they can be punched out of strip material, wherein a mounting device can simultaneously press several contact nails into the underside of a carrier plate.

In fact, it has been known to derive signals from a carrier plate with conductive openings through sheet metal pieces, which are inserted into the openings (cf .. EP 0 448 483 A1, US 3,871,728 A, US 4,828,515 A, US 5,145,408 A). Contact nails, which are suitable as a replacement for solder balls, but are so small that one could not assume that the difficulties in their handling would be more than offset by the advantages of the construction achieved.

Further details of the invention will be explained with reference to the drawing.

In this, Fig. 1 is the perspective view of a contact nail. 3 shows the underside of a carrier plate with a plurality of pressed-in contact nails, FIG. 4 shows a section through the carrier plate in the scale of FIG. 1 in the region of an opening of the carrier plate, FIG. 5 shows a top view on the support plate according to FIG. 4.

The in Fig. 1 illustrated contact nail 1 consists of a square cross-section shaft 2 and a semi-circular head. 3 Such contact nails 1 can be easily punched out of a band 4, wherein it is advantageous not to isolate the contact nails 1 immediately, but as shown in FIG. 2 represented by a predetermined breaking point with the band 4 in combination. An automatic assembly machine, which detects the position of the contact nails 1 via holes 5, can then remove several contact nails 1 at the same time and press into the bottom of a support plate 7, as shown for example in FIG. 3 shown. Usually, the contact nails form the crossing points of a grid, this grid as shown in FIG. 3 may be in the form of a frame or a large area and not all grid points with contact nails 1 must be equipped.

As shown in FIG. 4 5, support plates for chips and other ICs are usually multilayered. At the top of the support plate 7 thereby run conductor configurations with which the outer terminals of the ICs are connected. These conductor configurations in turn lead back to usually the crossing points of a grid forming openings. 6 The walls of these apertures are lined with conductive material, with gold, silver, and tin-lead alloys being proven as lining materials.

In the recesses 6 now contact nails 1 are pressed from the back of the support plate 7, which are notched with their shank edges in the walls of the openings 6. This creates a gas-tight connection.

The contact nails 1 themselves can be made of different materials, which are suitable for the preferred production by punching especially bronze and nickel silver. For example, SnBz 8 or NS 6218 would be considered as the base material. The surface of the punched nails is preferably tempered with a nickel-silver, a nickel-gold or a lead-tin alloy.

AT 401 704 Β

The contact nails according to the invention have a whole series of advantages. They are cheap to produce and cheap and precise to process. They are used regardless of the material of the carrier plate, temperature resistance up to 160 * 0 is given. Due to the high thermal conductivity short-term heat effects are well weathered, where the usual solder joints would be damaged already. The fact that the material of the nails during the reflow process on the base plate (motherboard) retains its shape, an absolute coplanarity between the back of the support plate and the solder paste coated base plate is not required. Quite apart from this, the proposed contact nails in any case by a measure on the back of the support plate, which is much more precise than in the case of solder balls.