Cu/Low-k TBGA Glob Top Package Reliability Challenges

Moving into low-k die packaging era, due to much weaker mechanical properties and poorer adhesion of interlayer dielectric, package reliability always poises a challenge to backend assembly process. This is especially critical for the cavity down Tape Ball Grid Array (TBGA) package. This paper discusses the approach taken to identify a feasible combination of material set and also the various process and design aspects that are important to lessen the overall package stress exerted onto the low-k die during reliability stress, primarily during temperature cycle test. Series of evaluations were conducted to derive a proven good solution for 44um fine pitch wire package and for Pb-free requirement.