Formation of AuSnx IMCs in Sn3.5Ag0.75Cu micro-solder joints fabricated by laser and hot air reflow processes
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The present study aims to investigate morphology and distribution of AuSnx IMCs (Intermetallic Compounds) in laser and hot air reflowed micro-solder joints. Diameter of Sn3.5Ag0.75Cu solder balls used in the experiments was 120 μm. Thickness of Au surface finish on pads of the joints was 0.1, 3.0 or 4.0 μm. In solder joints fabricated by the laser reflow (LR) process, most AuSnx IMCs were in needle-like or dendritic shape, and located near interfaces of solder and pads. Whereas, the AuSnx IMCs within the solder joints fabricated by the hot air reflow (HR) process presented in fibrous or faceted shape, and distributed all over the solder joints. Diversity of morphology and distribution of AuSnx IMCs in the LR and HR solder joints is caused by different characteristics of heat source, different solidification rate of solder joints, and different reaction time between Au and Sn in the two reflow processes.
KeywordsSolder Joint Solder Ball Under Bump Metallization Reflow Process Sharp Temperature Gradient
This work is financially supported by the National Natural Science Foundation of China (Grant No. 51005058) and Natural Scientific Research Innovation Foundation in Harbin Institute of Technology (HIT. NSRIF. 2009037).
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