After the Material A-to-Material B delamination in the package was eliminated, the high Z-expansion of Material
A compared to EAC and the rest of the core caused high “bulging” over the bumping area during chip-attach (CAM) reflow.Fig.10 shows a schematic of the bulge of the EAC cavity material at high temperature. Clearly, the solder resist directly above the EAC cavity will show high Z-displacement at reflow temperature affecting the FLI joint.