PROPERTIES AND RELIABILITY OF LIQUID EPOXY-RESIN FOR LSI FABRICATION WITH THE PRINTING ENCAPSULATION SYSTEM (PES)

With the development of portable equipment such as IC cards, LCDs, cel lular telephones, and notebook computers, the recent trend of LSI pack aging has been a rapid movement toward increased thinness and the adop tion of chip-on-board (COB) designs. The conventional transfer molding technique has difficulty in meeting these requirements. It also has e conomic disadvantages such as high die cost, resin loss in the runners and sprue, and long processing time. This paper describes the printin g encapsulation system (PES), developed as a replacement for transfer molding in LSI processing. The technique is suited to mass production, is readily applied to packages less than 1 mm thick, and is economica lly effective, since it does not require expensive dies and has minimu m resin loss. The resin used in PES is liquid epoxy, which must have g ood thixotropic stability after printing and curing. High-purity silic a microparticles are an effective thixotropic agent that can tolerate long printing times. To prepare for the future production of larger LS I packages, stress reduction is achieved by using silicone resin to mo dify the epoxy. The reliability of a 10 x 10 mm LSI prepared with this modified epoxy resin was tested on a ball grid array (BGA) package an d was found to be highly reliable. The use of the PES technique and th e low-stress epoxy resin should make it possible to extend the applica tion to many new types of packaging, such as BGA, PLCC, CSP, MCM, TAB, and the like. (C) 1997 Scripta Technica, Inc.