New type LOC adhesive tapes

A new technology of the plastic package is offered in volume production of 16 Mb DRAM. This new package, called the LOC (Lead On Chip) structured package, is characterized by directly bonding the lead frame to the surface of the chip with a adhesive tape. This technology requires some new type packaging materials. Adhesive tape is the key material used in the LOC structure package. We developed the polyimide siloxane as the adhesive for the LOC adhesive tape. The polyimide siloxane has several advantages for use in the LOC adhesive tape, namely, small amount of outgassing volatiles, low content of ionic impurities, low moisture absorption and significant bendability. Moreover, the glass transition temperature of polyimide siloxane adhesive can be controlled over a wide range from 100 to 220°C by controlling the content of the component especially the silicone. The single layer adhesive tape which had no base film and was constructed only of the polyimide siloxane was manufactured by the casting method. This single layer structure can enhance the advantage of adhesive polyimide siloxane and reduce the problems due to the interface of adhesive and base film. Actually, the single layer structured LOC tape has the outstanding advantage of low moisture absorption, so can solve the problem of delamination which occurs at the various interfaces of LOC tape and the other materials in the DRAM package