Impact of substrate surface condition and epoxy mixture properties on the overflow/incomplete flow

We have investigated different factors which affect the capillary flow behavior of epoxy mixtures to cause failure modes such as overflow/incomplete flow issues during a chip package process. Stability of epoxy mixture fluidness and substrate surface roughness have been revealed to significantly affect the flow behavior when compared with other factors. Based on the investigation results, we rank the impact factors which affect flow behavior of epoxy mixtures by: stability of epoxy mixture fluidness ≈ substrate surface roughness > viscosity variation of epoxy mixtures caused by external shear force > viscosity variation of epoxy mixtures caused by dispense temperature > variation of wettability caused by both from different substrate vendors and different substrate positions > surface tension variation of epoxy mixtures.