Daichen Fu
Process Engineering Operations Manager, Schweitzer Engineering Laboratories
Thursday, April 26
11 a.m. – noon in ETRL 101
Refreshments served in ETRL 119 at 10:30 a.m.
Lead-Free BGA Mixed Soldering Study
Abstract
This study is to evaluate different process combinations to solder Pb-free BGA under SnPb solder environment. Four variables are included in the full factorial experiment design, PCB finish type, paste/flux type, BGA ball composition and BGA package type. An elevated temperature reflow profile is used for all test groups. Thermal cycling and board bending tests are performed. Results show when HASL finish is used, all mixed soldered Pb-free BGA with SnPb solder paste are able to sustain at least 1,000 thermal cycles. There are early failures before 100 cycles, they are all from ENIG finish boards. The cause of early failures is insufficient formation of inter-metallic compound on the interface between ENIG finish and mass solder. Board bending test also shows much higher percentage of open circuits on ENIG finishing boards.
This study finds the best process combination for Pb-free BGA is HASL finish with PBGA packages. SnPb paste or flux-only does not make significant difference. CSP type packages and low Ag content Pb-free alloy are generally less reliable than PBGA package with SAC305/405 alloy, but as long as HASL finish boards are used, there are no early thermal cycle failures.
Biography
Daicheng Fu is a Process Engineering Operations Manager with Schweitzer Engineering Laboratories in Pullman, WA. He received his M.S in Industrial Engineering from Arizona State University and B.S in Mechanical Engineering from Shanghai Jiao Tong University. He has over twenty years of experience in electronics manufacturing, in both consumer electronics and high-reliability industrial control equipment. In SEL, Daicheng Fu has led several in-depth studies on quality and reliability issues, such as backward-compatibility issue with lead-free components in tin-lead soldering environment; component latent damage caused by board bending stress; tin whisker issue and prevention on lead-free components; and silver dendrite issue and prevention. Currently Daicheng Fu is leading SEL’s process engineering team in new process development; soldering material evaluation; New Product Introduction; and Design for Manufacturability improvement.
