Avoiding mechanical damage, such as die delamination, due to moisture-induced stress during the assembly solder reflow is a high priority for many package assemblers. Moisture/reflow sensitivity classification allows board assembly operations to exercise proper storage and handling precautions to avoid damage caused by moisture. The choice of materials and optimization of process parameters can significantly influence the moisture sensitivity classification of chip packages. This paper directly compares two types of heat spreaders and two types of adhesives used in a cavity-down nonhermetic organic wire bond package. Specifically, a nickel/gold plated copper heat spreader with a glass cloth reinforced, silver-loaded epoxy thermoset film is contrasted to a heat spreader treated (zincated) on the side facing the substrate with nickel plating on the opposite side, and bonded with an epoxy/acrylate hybrid thermoset adhesive film filled with silver coated glass particles. The responses analyzed include voiding and delamination as determined by reflective C-mode Scanning Acoustic Microscopy (C-SAM), and visual analysis for cracks.
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