Method of bonding polyimide films

Claim 1

THE METHOD OF CURING A RAW ADHESIVE FILM CONSISTING ESSENTIALLY OF A POLYAMIC ACID CONFINED BETWEEN TWO BARRIER LAYERS AT LEAST ONE OF WHICH HAS POROSITY OF WATER VAPOR AND FOR RESIDUAL SOLVENT IN SAID RAW ADHESIVES, SAID METHOD COMPRISING: (A) SUBJECTING A FILM OF EXPOSED RAW ADHESIVE TO A TEMPERATURE IN THE RANGE OF BETWEEN ABOUT 250*F.350*F. FOR A PERIOD OF SEVERAL MINUTES AND THEREAFTER SLOWLY DECREASING THE TEMPERATURE TO A RANGE OF BETWEEN ABOUT 200*F. TO 250*F.; (B) EXPOSING SAID FILM TO A SECOND TEMPERATURE IN THE RANGE OF ABOUT 300*F.-500*F. FOR A PERIODD OF ABOUT 1/4 TO ABOUT 3 MINUTES, AND TACKING SAID FILM TO A SURFACE OF A MEMBER TO BE BONDED THERETO WHILE AT SAID ELEVATED TEMPERATURE; (C) POST-CURING SAID ADHESIVE FILM BY EXPOSURE TO A TREATING ZONE WHEREIN THE TEMPERATURE INCREASES AT A SLOW RATE FROM ABOUT 250*F. TO ABOUT 450*F., SAID EXPOSURE BEING CONTINUED FOR A PERIOD OF BETWEEN ABOUT 3 TO 8 HOURS.