Analysis of Package Cracking During Reflow Soldering Process

Abstract

Surface munt packages are heated up above solder melt ing temperature during reflow soldering process. If t h e p l a s t i c e n c a p s u l a n t h a s absorbed m o i s t u r e , package cracking may occur. In t h i s study, an evaluat i o n method of Lhe package cracking is developed by means of moisture diffusion analysis of p l a s t i c and deformation and s t r e s s analysis of packages.

Integrated vapor pressure, hygroswelling, and thermo-mechanical stress modeling of QFN package during reflow with interfacial fracture mechanics analysis

“…Therefore, it is critical to evaluate the strength of internal vapor pressure generated in the package during reflow. The popcorn failure was first postulated by Fukuzawa et al [3] in 1985, and later supported by many publications [4][5][6].…”

“…Kitano et al [5] showed that the package cracking is not controlled by the absolute moisture weight gain, rather it is due to the local moisture concentration at the critical interface. Therefore, moisture diffusion modeling is required.…”

“…However, the modeling of ensuing vapor pressure within the package during the reflow is the key element in understanding the failure mechanism. Previous researchers [4][5][6] assumed that the delamination exists before the reflow, and considered the vapor pressure as traction loading subjected to the delaminated interfaces. There were some studies done and a few methods were proposed to estimate the vapor pressure acting on the delaminated interface.…”

Interface delamination analysis of TQFP package during solder reflow

“…Fick's second law can be applied to describe the moisture diffusion process in polymer materials [1][2][3][4][5][6][7][8][9][10][11][12][13]. According to Fick's second law, moisture diffusion in a material is defined by Fickian diffusion law in three dimensions as follows [23]:…”

“…Many investigations have shown the delamination phenomenon to be closely linked to the processes of heat transfer, moisture diffusion and vapor pressure build-up [1][2][3][4][5][6] during solder reflow. Manufacture induced small voids or defects in interfaces of plastic IC packages due to the thermal expansion mismatch of the packages generally become potential sites for delamination failure and may grow owing to hygrothermal stress concentration and water vapor pressure in the delamination.…”