A study of Sn-Ag-Cu solder interconnection behaviour under gamma radiation exposure

The resilience of microelectronic packaging to gamma radiation is a crucial factor in solder joint evaluation due to its impact on the reliability of electronics within radiation-prone environments. This study focused on tin-silver copper (Sn96.5Ag3.0Cu0.5; SAC305) solder joints durability due to extreme gamma radiation environment. The SAC305 solder were exposed to gamma radiation with doses ranging from 5 to 50000 Gy. The evolution of the microstructure, intermetallic compound layer growth, crystallographic structure of solder alloy and behaviour of micromechanical properties of SAC305 solder joint due to gamma radiation exposure was investigated. The microstructure and IMC layer images were captured using optical microscope and then analysed by using ImageJ software. The micromechanical properties of solder joint such as the hardness, reduced modulus and creep behaviour was determined using nanoindentation testing and analysed using Oliver-Pharr Method. As the gamma radiation dose increased, the IMC layer thickness increases due to heat-induced coarsening behaviour. The XRD results show the presence of the β-Sn, Cu6Sn5 and Ag3Sn phases. Micromechanical properties obtained from nanoindentation test indicated that the occurrence of wavy-pattern on the load-depth (P-h) curve. As radiation dose increased, the SAC305 solder transition from elastic to plastic. For the 0 Gy of SAC305 solder, the hardness and reduced modulus values were determined to be 0.26 GPa and 66.5 GPa, respectively. Prolonged exposure to gamma radiation leads to the coarsening of Ag3Sn, diminishing the strengthening effect of the compound and increasing dislocation mobility. The eutectic phase area showed a parallel trend to the hardness value obtained. Overall, gamma radiation significantly impacts microstructure, mechanical properties, and solder joint performance. Consideration of gamma radiation effects is essential in electronic package design for reliable operation in radiation-prone environments.