In the construction of semiconductor chip assemblies, it has been found desirable to place elastomeric materials between some of the various components. For example, in some of the structures disclosed in PCT/US91/06920 (filed Sep. 24, 1991) by I. Khandros and T. Distefano, the disclosure of which is incorporated herein by reference, a chip carrier includes a flexible dielectric layer with leads and an array of terminals. The chip carrier is fastened to a semiconductor chip or "die". An elastomeric material is disposed between the chip and the flexible dielectric layer of the chip carrier. The chip carrier and elastomeric material are also referred to as an "interposer". The leads of the chip carrier are bonded to the chip so that the terminals of the carrier are electrically connected to the contacts on the chip. The entire structure can then be mounted to a substrate such as a circuit panel or chip housing. The terminals of the chip carrier are electrically connected to contacts on the substrate. The elastomeric layer provides resiliency to the individual terminals, allowing each terminal to move as necessary to accommodate tolerances during testing and in the final assembly itself.
In some arrangements used heretofore, the elastomeric layer was formed by casting a silicone rubber resin onto a release liner and curing. Next, additional resin was applied to each side of the cured sheet, the additional resin was partially cured, and the resulting tacky adhesive surface was used to bond the elastomeric layer to the chip and chip carrier. Once attached, the entire structure was heated and fully cured.
Although this process is effective, further improvement would be desirable. The components are of small size and require instruments which are capable of handling such small components. Also, air can be occasionally entrapped when the chip carrier and die are affixed to the elastomer layer. The entrapped air can create defects. Accordingly, care must be taken to prevent such entrapment. This adds to the expense of the process.
Accordingly, further improvement would be desirable.