材料期刊网

利用差示扫描量热分析法结合焊点回流过程, 研究了无Pb钎料Sn-3.5Ag与Cu基底构成的Sn-3.5Ag/Cu体系模拟焊点中早期界面反应及焊点形成过程中钎料熔化和凝固特性. 结果表明, 加热过程中Cu向钎料合金侧的固态原子扩散导致界面生成低熔点Sn-Ag-Cu三元合金, 使焊点界面在低于Sn-3.5Ag钎料熔点温度近4 ℃时即开始熔化; 早期界面反应促使润湿过程提早发生并生成了一定厚度的扇贝状Cu-Sn型金属间化合物(IMC), 原体系转变为 Sn-Ag-Cu/Cu体系；转变后的焊点体系在IMC的非均匀形核作用下具有较低的过冷度.

For electronic packaging technologies using lead-free solders, one of the major problems related to reliability for the solder interconnects is the existence of the interfacial intermetallic compound (IMC). The interfacial failures between IMC and solder alloy often lead to loss of function in interconnects and result in product failure. Therefore, considerable attention has been focused on study of formation, growth and control of IMC during solder process. In this paper, the early interfacial reaction in Sn-3.5Ag/Cu (UBM) system and the system's melting and solidification characteristics were investigated using differential scanning calorimeter incorporating with reflow process. The results show that during heating the diffusion of Cu atom into Sn-3.5Ag solder results in the formation of Sn-Ag-Cu ternary alloy at the interface before melting of Sn-3.5Ag solder and the ternary eutectic system melts at a temperature nearly 4 ℃ lower than Sn-3.5Ag solder's melting temperature. The early interfacial reaction also leads to earlier wetting of the liquid solder alloy at the interface, and consequently brings about formation of scallop-type Cu-Sn intermetallics layer with a certain thickness as well as makes the initial Sn-3.5Ag/Cu system changed into Sn-Ag-Cu/Cu system, which makes the undercooling of the solder alloy decrease obviously.