Thermoplastic film die attach adhesives

Claim 1

A thermally conducting, thermoplastic melt die-attach adhesive film, which softens at 200° C. but is firm at 175° C. to maintain adhesion, comprising: (A) a normally solid thermoplastic polyimide polymeric binder having a weight average molecular weight of about 100,000 to 150,000 and synthesized from: (1) an aromatic dietherdianhydride having the structure: ##STR14## in which K is a substituted or unsubstituted group of the formula: ##STR15## in which W is --O--, --S--, --SO 2 , linear or branched alkylene or alkenylene having 1 to 8 carbon atoms or --(R)C(L)--, in which R and L can be the same or different lower alkyls having 1 to 8 carbons or aryl groups having 6 to 24 carbon atoms, and m is 0 or 1; and (2 ) a meta-substituted benzenediamine having the structure: ##STR16## in which Y is a divalent unsubstituted meat-phenylene radical or a meta-phenylene radical substituted with at least one lower alkyl group containing 1 to 8 carbon atoms; T is selected from the group consisting of --O--, --S--, --SO--, --SO 2 , --CO-- and lower alkylene having 1 to about 6 carbon atoms; the benzenediamine present in an amount of about 20 to about 50 mole percent of the total diamine content of the polyimide polymeric binder; and (3) a polysiloxanediamine having the structure: ##STR17## in which Q is a meta-substituted arylene; Z is a divalent oxygen, sulfide, sulfone, sulfoxide or carboxylic ester or amide group; D is a hydrocarbylene group; R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are the same or different alkyls having 1 to 8 carbons; and x, y and z are integers having values of 0 to 100; the polysiloxane diamine present in an amount of about 80 to about 50 mole percent of the total diamine content of the polyimide polymeric binder; the dianhydride content and total diamine content present in an unequal molar ratio of diamine to dianhydride of 0.95-0.97:1; and (4) p-aminophenol present as an end-capping agent in an amount up to about 15% of the theoretical equivalents of excess anhydride functionality; and (B) thermally conductive material present in an effective amount up to 85% by weight of the die-attach adhesive film to provide a conducting medium.