Microcircuit package assembly utilizing large size die and low temperature curing organic die attach material

Claim 1

An ASIC type microcircuit package assembly which comprises: a die at least about 20 millimeters square in size; a substrate for said die; a polymeric die attach containing a conductive filler and forming a bond between said die and said substrate, said bond capable of sustaining temperatures of up to at least about 360° C. and stress conditions corresponding to a 12 pound pull following 1,000 temperature cycles between -65° C. and 150° C. after curing of said die attach at a temperature of about 100° C. to 150° C.; and means for hermetically sealing said die bonded to said substrate with a moisture level of less than about 5000 ppm, wherein: said die attach comprises about 10 to 40 wt % of a cyanate ester vehicle and about 60 to 90 wt % of a conductive filler; said cyanate ester vehicle comprises a liquid cyanate ester having a viscosity of about 1 to 5 poise at 25° C., about 2 to 6 pph of an alkylphenol, and about 50 to 500 ppm of a catalyst; said filler comprises particulate material of less than 70 microns; said die attach has the capability of being cured in about 30 minutes to about 1 hour; and said die attach has a viscosity of about 100 to 1000 poise at 25° C.