Abstract:

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 85^oC and 30% relative humidity followed by simulated Infrared reflow at temperature ramp rates of 1^oC/s and 0.67^oC/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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