Drop test reliability assessment of leaded & lead-free solder joints for IC packages

With the development of smaller and higher density surface mount packages like Quad Flat No-lead (QFN) and Ball Grid Array (BGA), solder joints strength of the electronic components has a greater impact on the reliability of an end product. And the decrease in size of consumer products such as cellular phones, PDAs, and MP3 players has increased the frequency of accidental drops resulting in solder joint cracks and eventually malfunction of the products. With legislation put in place by government and industrial bodies, electronics companies are driven to eliminate the uses of Lead in their products. It thus leads to the concern of reliability of lead-free solders as interconnects. The present work aims at studying the effects of drop impact on the reliability of solder interconnects of leaded (36Pb62Sn2Ag) and lead-free (Sn4Ag0.5Cu) compositions. The influence of different package types and the impact of PCB surface finishes of OSP and ENIG (electroless nickel immersion gold) have also been looked into. The drop test results has shown that lead-free solder joints on the ENIG finish have weaker drop reliability performance compared to the leaded and lead-free solders on an OSP finish.