Moisture induced delamination between plastic encapsulant and substrate can lead to catastrophic failure during electronic package manufacturing process. In this study, a set of interfacial characterization methodology and a steam driven delamination criterion C_dc was developed where C_dc is the critical moisture concentration at the defect surface. The influences of defect size, molding compound thickness and material properties are collected into a single relationship. The developed criterion C_dc can be used to directly compare with moisture concentration in the package to determine the design guideline for solder reflow and pre-bake processes. C_dc and the moisture concentration in the package are determined through experiments. _dc...[ Read more ]

Moisture induced delamination between plastic encapsulant and substrate can lead to catastrophic failure during electronic package manufacturing process. In this study, a set of interfacial characterization methodology and a steam driven delamination criterion C_dc was developed where C_dc is the critical moisture concentration at the defect surface. The influences of defect size, molding compound thickness and material properties are collected into a single relationship. The developed criterion C_dc can be used to directly compare with moisture concentration in the package to determine the design guideline for solder reflow and pre-bake processes. C_dc and the moisture concentration in the package are determined through experiments.

C_dc is related to the critical strain energy released rate and is a function of the fracture load between glob-top and copper substrate and is experimentally measured using shear fracture test with interfacially pre-cracked specimens. The interfacial fracture energy is determined from the measured fracture loads using finite element analysis. The dependence of interfacial fracture energy on temperature is discussed. A novel characterization technique of evaporation rate from water saturated epoxy by thermogravitic analysis (TGA) is developed to determine the engineering rate of water evaporation from polymer encapsulant. The result of the evaporation experiment indicated that the conventional estimate of water evaporation using saturation pressure over-estimated the measured rate by nearly two orders of magnitude. The interfacial fracture energy released rate G_c, water diffusion coefficient D, and moisture evaporation coefficient F of a glob top/copper substrate system as a function of temperature are used to predict delamination failure during solder reflow and pre-bake process. The analysis revealed that the critical delamination temperature is mainly controlled by reflow conditions.

Based on the newly developed analytical plan and experimental scheme, time consuming trial an error testing can be much reduced. Engineers can make use of the measured adhesion data and the moisture absorption history of the selected encapsulant, and shoot for the optimal pre-baking and reflow profile.