Influence of Difference Solders Volume on Intermetallic Growth of Sn-4.0Ag-0.5Cu/ENEPIG

Abstract

Abstract. In recent years, portable electronic packaging products such as smart phones, tablets, notebooks and other gadgets have been developed with reduced size of component packaging, light weight, high speed and with enhanced performance. Thus, flip chip technology with smaller solder sphere sizes that would produce fine solder joint interconnections have become essential in order to fulfill these miniaturization requirements. This study investigates the interfacial reactions and intermetallics formation during reflow soldering and isothermal aging between Sn-4.0Ag-0.5Cu (SAC405) and electroless nickel/immersion palladium/immersion gold (EN(P)EPIG). Solder diameters of 300 μm and 700 μm were used to compare the effect of solder volume on the solder joint microstructure. The solid state isothermal aging was performed at 125°C starting from 250 hours until 2000 hours. The results revealed that only (Cu,Ni)6Sn5 IMC was found at the interface during reflow soldering while both (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 IMC have been observed after aging process. Smaller solder sizes produced thinner IMC than larger solder joints investigated after reflow soldering, whereas the larger solders produced thinner IMC than the smaller solders after isothermal aging. Aging duration of solder joints has been found to be increase the IMC's thickness and changed the IMC morphologies to spherical-shaped, compacted and larger grain size.

Influence of Ni on the refinement and twinning of primary Cu6Sn5 in Sn-0.7Cu-0.05Ni

“…Similar to the (Cu,Ni)6Sn5 reaction layer, Ni additions significantly influence the formation of primary Cu6Sn5 in the bulk solder. Solders containing nickel usually have significantly smaller and more numerous primary Cu6Sn5 rods/particles in the bulk solder compared with Ni-free solders [14,[32][33][34][35][36][37][38]; and various papers on Ni-containing solders contain micrographs of primary Cu6Sn5 crystals with an X-shaped morphology [10,[39][40][41][42].…”