A comparative study of conventional reflow and microwave hybrid heating reflow of Sn-3.0Ag-0.5Cu/Cu solder joints

Purpose This study aims to compare wettability, interfacial morphology and mechanical properties of Sn-3.0Ag-0.5Cu (SAC305) solder on Cu substrate using conventional reflow (CR) and microwave hybrid heating (MHH) methods. Design/methodology/approach The solder paste was reflowed using a conventional reflow oven set to 250°C for 6 min, while MHH was conducted using medium microwave power mode for 2 min with a silicon wafer as a susceptor. Wettability, phase formation, morphology and mechanical properties were analyzed using scanning electron microscopy, X-ray diffraction, ImageJ and Vickers hardness test. Findings MHH significantly improved solder wettability by exhibiting a 42.46% lower wetting angle and a 7.73% higher spreading ratio compared to CR. Phase analysis identified the presence of Cu6Sn5 intermetallic compounds in both heating methods. The morphology showed a slightly thicker Cu6Sn5 layer in the MHH sample relative to the CR sample. Mechanical assessments revealed higher and more consistent Vickers hardness values for MHH reflowed solder, suggesting better mechanical uniformity across the joint. Originality/value This study presents a direct comparative analysis of wettability, phase formation, morphology and Vickers hardness of SAC305/Cu joints reflowed by CR and MHH. The findings highlight the influence of heating profiles on solder joint properties and offer comparative insights to guide optimization of reflow processes for reliable electronic packaging applications.