DIRECT SURFACE MOUNT IC PACKAGE FOR PCB'S

THIS EFFORT WILL FOCUS ON LOWERING COST AND IMPROVING PER- FORMANCE BY ELIMINATING CERAMIC AND PLASTIC PACKAGES PRES- USED IN SURFACE MOUNTING SEMICONDUCTOR CHIPS. THE CHIP WILL BE MOUNTED DIRECTLY TO A PREPARED FOOTPRINT ON THE PRINTED CIRCUIT BOARD (PCB) UTILIZING ADVANCED TAPE AUTO- MATED BONDING (TAB) AND NEW CHIP OVERCOATING MATERIALS. A COMMERCIALLY AVAILBLE VLSI SHIP WITH MORE THAN 60 I/O'S WILL BE SELECTED (THE PRIME CANDIDATE IS A CHIP WITH 136 I/O'S) TO BE TAB SURFACE MOUNTED TO PCB'S AND THEN OVER- COATED WITH SPECIALIZED ENCAPSULANTS. PRIOR TO EXCISE AND SURFACE MOUNTING, THE CHIP WILL BE PROCESSED WITH ELEC- TROPLATED GOLD BUMPS ON EACH CHIP BONDING PAD, THEN INNER LEAD BONDED (ILB) TO A 35MM FILM OF POLYIMIDE MATERIAL TO WHICH COPPER FOIL HAS BEEN LAMINATED, AND THE APPROPRIATE CIRCUIT PATTERN ETCHED AND GOLD PLATED. THE ILB PROCESS IS ACCOMPLISHED WITH GANG BONDING, A SINGLE OPERATION THAT BONDS ALL OF THE CIRCUIT LEADS TO THEIR ASSIGNED BONDING PADS. THE SURFACE MOUNTED AND OVERCOATED CIHIP- ON-BOARD WILL BE TESTED AND EVALUATED FOR ENVIRONMENTAL AND