To types of plastic ball grid array packages, a 225-lead full matrix.
array and a 256-lead perimeter, array, ere subjected to 168 hours of moisture
preconditioning at 85oC and 30% relative humidity followed by
simulated Infrared reflow at temperature ramp rates of 1oC/s
and 0.67oC/s. The packages ere subsequently examined for delamination
and cracking using scanning acoustic microscopy and environmental scanning
election microscopy. At the higher, ramp rate, delamination and cracking
, were observed in both package types, originating i, the die attach and
propagating along the weakest interfaces. At the lower ramp rate, a small
amount of delamination was observed. This suggests that there is a critical
ramp rate below which popcorn cracking does not occur.
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