Investigation of Interfacial Behavior of SN100C and SN97C Solders with HASL Surface Finish Using Microwave Energy

The growth of intermetallic compounds (IMCs) of HASL/SN97C (Sn-3.0Ag-0.5Cu) and HASL/SN100C (Sn-0.7Cu-0.05Ni-0.007Ge) during reflow soldering and isothermal ageing was investigated. Scanning electron microscopy (SEM) was used for the characterisation examination of the materials, with assistance from dispersive X-ray analysis. New layer IMC of Cu3Sn formed between Cu6Sn5 and the HASL substrate after exposure to the ageing process, while Ag3Sn nano-sized was also formed on the intermetallic surface of HASL/SN97C. After ageing, the intermetallic layer's average thickness increased. The IMC produced at the HASL/SN100C interface after reflow and ageing process had an average thickness of 6.54 µm and 8.50 µm, respectively. While the thickness of the IMC created after reflowing and ageing is 7.41 µm and 8.53 µm correspondingly for HASL/SN97C. Based on the observation, after the ageing procedure, the IMC thickness for both HASL/SN100C and HASL/SN97C increases. The results found that both SN97C/HASL and SN100C/HASL had contact angles of 26.64° and 35.76°, respectively. The spreading area in SN97C/HASL (976.68 µm) was significantly larger than that in SN100C/HASL (233.26 µm) due to the lower contact angle.