The plastic deformation of solder occurs during the procedure of thermal compression bonding. The lower stress applied by using soft material is thus anticipated. The present study investigated the softening effect of polyethylene glycol (PEG) 6000 on micro Sn electrodeposition. The grain size, thickness, surface roughness (Ra), interfacial reactions and phase evolution of Sn deposit on Cu substrate were investigated to find their effects on mechanical properties. The Sn deposit obtained without PEG addition exhibited the highest hardness and elastic modulus due to the grain refining effect. With 0.15 g/L PEG addition, the significant drops of hardness and elastic modulus of deposition were 80.5% and 87.7% under 4 mA/cm2 while as 66.1% and 67.9% under 5 mA/cm2. The softening Sn deposit was attributed to the grain growth when adding PEG in electroplating bath. With appropriate PEG addition, the high portion of Cu6Sn5 produced in the deposit was responsible for the relative high mechanical properties.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials