Preparation Of Lead-free Solder Paste And Reliability Evaluation Of Board-level Package

Compared to leaded Electronic devices, lead-free electronic devices both in thephysical and mechanical properties and in terms of reliability are different, it needsfor depth research. With the rapid development of SMT technology, makes mobilephones, cameras, MP3players, laptops and other products are handheld,miniaturization, compared with traditional electronic products, these types ofelectronic products whose life cycle is short, fast replacement, Therefore, failure dueto temperature cycling is no longer the main failure reasons, in the process oftransport, storage and use, they are more vulnerable to unexpected vibration, impact,thereby causing the electronic device failure. Therefore, it is necessary to study thereliability of the electronic device under the conditions of the mechanical shock(vibration, drop, etc.).In this paper, the more mainstream of the three Sn-Ag-Cu lead-free solderSn-3.0Ag-0.5Cu, Sn-1.0Ag-0.5Cu and Sn-0.3Ag-0.7Cu and BGA device as theresearch object, combined with ABAQUS numerical simulation software, analysis theforce of board-level package devices in the case of vibration and drop, and contrastwith the actual vibration and drop test, Compare the life of different solder jointsunder conditions of vibration and drop, observed failure mode, analyze the failuremechanisms and silver content which have influence on the life of solder joint.The results show that：The life of the solder joints gradually improve with thereduction of the Ag content under the conditions of random vibration and drop, thelife of lead-free solder joints with three materials: SAC305<SAC105<SAC0307; Theposition of BGA solder joints in the chip has a great influence on their failure life,failure solder joints general locate at the outermost edge of the BGA,Cracks alongIMC which near the side of the PCB, it is consistent with the results of numericalsimulation; the thickness of IMC is characterized：SAC305> SAC105> SAC0307; thelower the Ag content of the brazing material, the intermetallic compound(IMC) afterwelding is thinner, and the morphology is different from that solder joints which ofthe high silver content; In front of low Ag solder IMC, there are many small Ag3Snparticles. The formation of Ag3Sn particle can reducing (Cu, Ni)6Sn5’s surface energy,and restrain the growth of the interfacial IMC.