Integrated circuit packaging using flexible substrate

Abstract

A multilayer, flexible substrate upon which integrated circuit chips can be attached is disclosed. The input/output(I/O) connections from the chip do not radiate outward from the side of the die, but rather extend from a bottom surface. Since the I/O signal lines would not be accessible for testing once the IC chip is mounted on a substrate, each I/O line is extended outward from the IC footprint to an area on the substrate which is accessible. Additionally, an electrical path from each I/O signal port is simultaneously passed through the substrate layers upon which the chip is mounted, thus providing electrical contact of all I/O ports to the underside of the flexible substrate. An integrated circuit chip is mounted on this flexible substrate. Since each I/O line is accessible after mounting, the IC chip can be tested prior to mounting on its ultimate carrier. Once tested, the IC chip and the substrate upon which it is mounted are excised from the roll of substrate material. This excised, pretested memory package, which includes both the IC chip and the flexible substrate, can then be mounted directly onto the ultimate carrier either by reflow soldering or direct bonding.