Effects of inter-metallic compound on high temperature reliability of flip chip interconnects for fine pitch applications

Solder joint is a method widely used to attach electronic chip on substrate. It is a generally knowledge that solder joint contains inter-metallic compound (IMC) at interconnects of solder bump and copper pads. The magnitude of IMC layer thickness impacts reliability of chip level packages. Extensive experimental investigations are conducted, however complementary numerical studies are needed to fully characterise the effects of IMC on high temperature reliability of flip chip (FC) assembly. In this work, thermo-mechanical response of FC lead-free solder joints to accelerated temperature cycle (ATC) is investigated using finite element analysis (FEA) code. The ANAND´s model is employed to study the inelastic, nonlinear, rate dependent and visco-plastic behaviour of two models of FC48D6.3C457DC mounted on printed circuit boards (PCBs). While one model consists of conventional joints without IMC, the other is realistic with IMC embedded. In the result analysis based on damage indicators such as induced strain, stress, plastic work and hysteresis, it is found that negative impact of IMC on static structural integrity of solder joint operating at high temperature ambient is nontrivial.