SnAgCu solder interconnection behaviour under gamma radiation exposure

Radiation particles with enough energy to break the chemical bonds of the materials, such as gamma radiation, may affect the performance of the device. In this research, the physical, mechanical properties and microstructure evolution of lead-free solder joints radiated with gamma radiation were investigated. Prior to characterization, the solder paste of tin-silver copper (SnAgsCuo.s; SAC305) was manually deposited on the printed circuit board using a stencil printing method and reflow soldering process. Subsequently, the solder was exposed to gamma radiation. As the gamma radiation dose increased, the thickness of the intermetallic compound (IMC) layer of the solder increased, and the contact angle remained to have good wettability. The nanoindentation test revealed the occurrence of pop-in events due to the atomic distortion and dislocation density of the SAC305 samples. The hardness and reduced modulus values increased up to 500 Gy owing to the disturbance in the atomic arrangement of the solder material. However, the values decreased as the radiation dose increased (5000 Gy) which could be linked to the presence of voids and heterogonous IMC. The eutectic phase area showed a parallel trend to the hardness value obtained. Field Emission Scanning Electron Microscopy and Energy Dispersive Spectroscopy analysis found that Cu6Sn5 and Ag3Sn compounds dominated the intermetallic layer in the Sn matrix. It is believed that heat released by gamma radiation changed the nature of solder materials from elastic to plastic as well as coarsen the microstructure and increased the IMC thickness. Therefore, the effect of radiation on microstructural properties of solder should be considered when used in radiation-related applications.