Novel high performance no flow and reworkable underfills for flip-chip applications

摘要

Flip-chip interconnect is the emerging technol- ogy for the high performance, high I/O (lnputs/Outputs) IC devices. Due to the thermal mismatch between the sili- con IC (CTE=2.5 ppm/0 C) and the low cost organic sub- strate such as FR-4 printed wiring board (CTE=18-22 ppm/deg. C), the flip chip solder joints experience high shear stress during temperature cycling testing. Underfill en- capsulant is used to couple the bilayer structure and is critical to the reliability of the flip-chip solder joint inter- connects. Novel no-flow underfill encapsulant is an at- tractive flip-chip encapsulant due to the simplification of the no-flow underfilling process. To develop the no-flow underfill material suitable for the no-flow underfilling process of flip-chip solder joint interconnects, we have studied and developed a series of metal chelate latent cat- alVsts for the no-flow underfill formulation. The latent catalyst has minimal reaction with the epoxy resin (cyclo- aliphatic type epoxy) and the crosslinker (or hardener) at the low temperature (