In this study, the brittle fracture of intermetallic compound (IMC) between low-Ag SnAgCu (SAC) solder and under bump metallization (UBM) under high-speed pull condition is studied for wafer-level chip-scale packages (WLCSP). The fracture morphology and fracture mechanism of IMC are analyzed by SEM, EDX and deeply etching techniques. Also, the forming mechanism of IMC and the relation with joint strength are investigated. The effects of high-temperature (HTS) aging on the fracture performance of IMC are examined. Results show that compared with keeping time, storage temperature is a much more important influencing factor on the formation of IMC and soldering joints strength. Cu content in the solder is another key influencing factor as well.@en

To enhance the ability of lead-free solder joint to resistfailures induced by mechanical impact and shock, someresearchers have introduced low-Ag lead-free solder. In thisstudy, the formation and evolution of IMC, the fracturemorphology and performance of solder joint between SAC105 solder and under bump Metallization (UBM) have beenstudied after different temperature storage aging and multireflowfor WLCSP. The morphology and fracture surface ofIMC have been analyzed by SEM, EDX and deeply etchingtechniques. The behavior of IMC and correlation withfracture mode of joint at high speed ball pull (HSBP) test hasbeen investigated. It has been found that high temperaturestorage (HTS) aging results in IMC growing from one layerthat is (Cu6Sn5) IMC to two different layers that are((Cu,Ni)6 Sn5 and (Cu,Ni)3Sn4). Multi-reflow results in theIMC layer thickness increasing a little and some needle-likeIMC grain spalling into the solder.@en