Experimental and numerical study of moisture effect on warpage of plastic package

摘要

In this paper, the moisture effect on the warpage of plastic package is studied through experimental and numerical method. Many investigations have proved that polymer materials can expand after absorbing moisture. And coefficient of moisture expansion (CME) is proposed to quantitatively describe polymer expansion caused by moisture. The plastic package consists of epoxy molding compound (EMC) and PCB, both of which can easily absorb moisture. Since different amounts of moisture absorption in different materials can lead to different expansions, warpage of plastic package can change after moisture absorption, even when the temperature keeps constant. Both the warpage and moisture are monitored during a series of processes. And the results show similar changing trend. The CME of EMC and BT core is tested through TGA/TMA method. It is found that the CME increases with temperature. Moisture diffusion simulation is used to determine the moisture concentration change of EMC and BT core during the ambient storage. The results combined with CME are used to calculate the warpage change caused by moisture during the ambient storage. The simulation results agree with the experiments, verifying the moisture effect on warpage.