Patterned adhesive flip chip technology for assembly on polyimide flex substrates

Abstract

This paper describes research conducted to develop and evaluate isotropically conductive adhesive preforms for the assembly of dice onto polyimide flex circuit based MCMs and single chip packages. The preforms are fabricated by screen printing complimentary dielectric and silver filled epoxy patterns corresponding to the die I/O pattern. The dielectric pattern provides a built-in underfill, eliminating the need for a post die placement underfill process. The silver filled epoxy dots provide the electrical connections. The preforms are produced in volume as a multi-up array printed on a release film. In the assembly process, the preform is first aligned and adhered to the die surface. Next, the dice and preform are aligned to the corresponding flex substrate pattern and bonded. The epoxy is then cured to complete the process. High temperature storage, temperature/humidity storage, and thermal cycling results are presented in this work.