The Effect of Polymer Rebound on SnBi58 Solder ACFs Joints Cracks during a Thermo-Compression Bonding

In this study, a novel thermomechanical analysis (TMA) method was introduced to measure the exact polymer rebound amounts due to pressures removal after a thermo compression (TC) bonding process. Polymer resin was laminated between two silicon chips (7*7mm
²
), and then the compressive mode TMA measurement was done on the prepared samples. Constant compressive pressures were applied until the temperature was gradually increased to target temperature, and the forces were removed at the target temperatures. The polymer rebound was measured by monitoring the z-axis dimension change after the compressive forces was removed. The effects of bonding temperatures (from 150 to 250 °C) and the bonding pressures (1, 2 and 3MPa) on the SnBi58 (139 °C melting point) solder joints morphologies and joint resistances were evaluated to optimize bonding conditions and remove solder joint cracks for low Tg acrylic-based solder ACFs applications.