Thermal-mechanical reliability analysis of WLP with fine-pitch copper post bumps

Abstract

Purpose This study aims to investigate the several parameters in wafer-level packaging (WLP) to find the most critical factor impacting the thermal fatigue life, such as the height of copper post, the height of solder bump, the thickness of chip. The FEA results indicate the height of solder bumps is the most important factor in the whole structure. Design/methodology/approach The copper post bumps with 65 µm pitch are proposed to investigate the thermal-mechanical performance of WLP. The thermal cycle simulation is used to evaluate the reliability of WLP by using finite element analysis (FEA). Taguchi method is adopted to obtain the sensitivity of parameters of three-dimension finite element model, for an optimized configuration. Findings It can be found that the optimal design has increased thermal fatigue life by 147% compared with the original one. Originality/value It is concluded that the finite element simulation results show outstanding thermal-mechanical performances of the proposed 65 µm pitch copper post bumps of WLP, including low plastic strain, high thermal fatigue life, which are desired for mobile device.

Design criteria for pad and stencil with high pick-and-Place yield

“…As abovementioned, the standard deviations of solder paste deposition volume and component assembly yield are the Smaller-the-Best characteristic and the Larger-the-Best characteristic of Taguchi quality (Sun et al , 2020; Huang, 2018; Martinek and Krammer, 2018), respectively, thus, the S/N under various parameter combinations are calculated by equations (1) and (2), respectively. The average SN ratio of various control factors under various levels is calculated, and the response table and response graph are shown in Figure 5, respectively, to show the influence of various factors on quality characteristics.…”