As a result of a global movement away from using Lead (Pb) in electronic assemblies, component manufacturers are almost exclusively providing lead-free parts to satisfy the high volume consumer markets. Unfortunately, relatively little is known about the performance of lead-free solders in harsh vibration and shock environments. These concerns are amplified because the consumer industry is currently evaluating another generation of lead-free solder alloys in an effort to improve reliability. Tin whiskers not withstanding, nearly all the current lead-free electronic piece-part termination finishes are compatible with tin-lead assembly solder with the exception of ball grid arrays. Reprocessing lead-free BGAs with tin-lead ball metallurgy is one means of mitigating the risk of lead-free solder material failure modes such as tin whiskers, high cycle fatigue, printed circuit board pad cratering, and intermetallic fracture. In addition, because qualification of a metallurgy change in a high reliability application can take years, BGA reballing allows original equipment manufacturers to maintain the certification and qualification status on existing configurations while managing the on-going lead-free alloy changes occurring on BGAs. In the present work, an assessment of the mechanical integrity of four different commercially available BGAs was evaluated after reballing using visual inspection, cross-section evaluation, scanning acoustic microscopy, moiré interferometry, ball shear, ball pull and assembly level thermal cycling.
Key Words: Lead-free, Ball Grid Array, Solder, Reliability, Electronics, Reballing