Thermomechanical behavior of organic and ceramic flip chip BGA packages under power cycling

Abstract

Numerical and experimental techniques were employed to assess the thermomechanical behavior of ceramic and organic flip chip packages under power and accelerated thermal cycling (ATC).In power cycling (PC), the non-uniform temperature distribution and different coefficient of thermal expansion (CTE) of each component make the package deform differently than in the case of ATC. Conventionally, reliability assessment is conducted by ATC that assumes uniform temperature throughout the assembly. This is because, ATC is believed to be a worse case condition compared to PC, which is similar to the actual field condition.In this work, for ceramic and organic flip chip ball grid array (FC-BGA) package, numerical simulations of ATC and PC were performed by combination of computational fluid dynamics (CFD) and finite element analyses (FEA). For PC, CFD analysis was used to extract transient heat transfer coefficients while subsequent thermal and structural FEA was performed with heat generation and heat transfer coefficient from CFD as thermal boundary condition. The numerical simulations were compared with in-situ, real-time moiré interferometry experiment. It was found that for certain organic packages, power cycling was more severe condition that causes solder interconnects to fail earlier than ATC while ceramic packages fail earlier in ATC than PC. Accordingly, qualification based on ATC testing may overestimate the life of the package.

Fluxless bonding of silicon chips to ceramic packages using electroplated Au/Sn/Au structure

“…In MEMS and some electronic packaging, Si chips are attached on ceramic packages which provide mechanical support, heat dissipation, and environmental protection [1][2][3]. Common ceramic packaging materials are composed of more than 90% alumina and have a nominal coefficient of thermal expansion of 7 ppm/°C.…”