Numerical Simulations of Joint-to-Joint Temperature Variation During Thermo-Compression Bonding

Thermo-compression bonding (TCB) is an important electronic packaging process which applies heat and pressure to form arrayed interconnections in simultaneity. TCB processes need to be optimized to ensure low thermal variation in order to produce uniform and reliable bonds. Due to the form factors and complex structures involved in TCB, it is difficult to determine thermal variations during bonding. We have developed finite element (FE) models to validate the thermal responses of an 8 × 8 Au-bumped microsensor array used during an experimental TCB procedure. This paper presents an analysis of the thermal distributions extracted from the FE models. As expected, the bumps are always warmer than the sensor locations for each bump because the source of heat is above the bumps, and the bumps are above the sensors. The difference is largest in the periphery bumps, up to ≈23 °C, and smallest in the center, down to ≈18 °C. While the simulated sensor temperatures have a range of ≈6.5 °C, the bump temperature range is only ≈2.2 °C. Furthermore, cross sectional analysis shows internal bump gradients to be up to 5.9 °C between top and bottom surfaces of each bump. These findings indicate that TCB can be a robust process with respect to thermal application.