Reliability of BGAs and Mixed Low Temperature Solder Assemblies

This paper presents two key aspects of reliability of ball grid array (BGA) technologies: one aspect for high-reliability (HR) and the other for commercial applications. For HR, it presents the effect of isothermal aging at BGA component level to address a burn-in requirement for die screening per Military standard specification. Pull and shear behavior of BGAs with tin-lead and SAC305 solder balls were presented for fresh and burn-in conditions (
$125^{\circ}\mathrm{C}$
and
$150^{\circ}\mathrm{C}$
for 240 hr). These were assembled onto PCBs and then subject to thermal cycling (TC) between
$40^{\circ}\mathrm{C}$
and
$105^{\circ}\mathrm{C}$
. Cycles-to-failures (CTFs) in Weibull plots were presented for the SnPb CABGA208 assemblies with micro-sectioned images, The commercial aspect covered low temperature solder ball and solder paste for assembling BGAs and other components. Two types of low temperature BiSn alloys, either Cu/Ni or Ag additives and with
$139^{\circ}\mathrm{C}/174^{\circ}\mathrm{C}$
solidus/liquidus temperatures, were evaluated. The mixed hybrid configuration utilized SAC305 BGAs using the SnBiAg solder paste. The low temperature assemblies were subjected to two TCs
$(-40^{\circ}\mathrm{C}/105^{\circ}\mathrm{C}$
and
$0^{\circ}\mathrm{C}/105^{\circ}\mathrm{C})$
. CTF results are presented for CABGA208 with failure analysis by X -sectional evaluation.