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The effect of different material parameters was investigated through experimental design methods. Delamination of the encapsulant from the encapsulant-chip interface and electrical continuity (wherever possible) were considered as response variables. Experimental results indicate that encapsulant, flux, pad metallurgy, solder mask, and die passivation influence the encapsulant's adhesion to the chip. Significant interactions between the flux and the pad metallurgy were observed. In addition, 'weaker' interactions were observed for the case of encapsulant-flux and encapsulant-pad metallurgy. The reliability of an encapsulated chip reduces drastically when thin boards (-18 mils) were used instead of thick (-62 mils) ones. Also, the parameter dependencies seem to be reversed for the case of thin substrates. The results are found to be in good agreement with Finite Element Modeling (FEM). Encapsulant delamination increases with a decrease in standoff height. Pad metallurgy significantly influenced the integrity of the solder joint. Assemblies with pads coated with Ni/Au showed earlier and faster electrical failures than pads coated with Organic Solderability Protective (OSP). Parameters influencing the underfilling of large die (>0.75") with tight pitch and low standoff were identified. The underfill quality was found to be very sensitive to the encapsulant's material properties, dispensing temperature and pattern.


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