Abstract: During the temperature change of reflow soldering, warpage deformation occurs in the plastic ball grid array package due to the mismatch of thermal expansion coefficients of different materials. A finite element method is used to simulate the warpage deformation behavior and stress strain of PBGA package, and the simulation results of warpage deformation are tested by shadow moiré method. The results show that the simulated values of the PBGA package warpage are very close to the measured values, which are respectively 35.9 μm and 36 μm. During the simulated reflow, the measured values of the warpage are consistent with the simulated values. During the reflow, the maximum thermal stress strain of the PBGA package is at the position of the substrate near the bonding layer, which is the biggest risk point for the thermal reliability of the PBGA package. The amount of warpage at the corners of the PBGA package is the largest, so the solder joints at the corners are also most prone to open-circuit, solder joint and other assembly defects.

Key words: plastic ball grid array package, warpage deformation, thermal stress-strain, finite element simulation, shadow moire method