Lead-free plastic area array BGAs and polymer stud grid arrays TM package reliability

Abstract

Many packaging and original equipment manufacturers (OEMs) have initiated a program of introducing lead-free electronics. Although lead usage in the packaging industry is relatively small, major efforts are ensuring to eliminate lead usage. In this context, we manufactured and qualified two “green” package solutions: lead-free low-profile fine pitch ball grid array (LFBGA) and polymer stud grid arrays (PSGA TM) area array packages. The primary source of lead in BGA is in the solder balls. Lead-free solder alloys are readily available, although there is no universal drop-in replacement identified so far for plastic BGAs. One of the most promising alloys for this purpose appears to be the eutectic Sn95.5Ag4Cu0.5, although it involves higher processing temperature. Based on a design of experiment (DOE), the best reflow profile has been determined and used. A lead-free 8×8 mm 2 LFBGA has been manufactured without other process or equipment changes, and has been qualified for JEDEC moisture level 3, with 245°C reflow simulations, and standard 1st level package reliability tests. An alternative to lead-free plastic BGA is the PSGA TM. The PSGA TM package consists of a polymer injection-molded 3D body with a location for chip mounting and polymer studs. The metallized studs, which are by nature lead-free, replace the solder balls within the BGA package. Moisture conditioning and reliability analysis was performed on 8×8 mm 2 PSGA TM. The package passed JEDEC moisture conditioning level 3 as well as standard reliability tests.