PBGA Popcorn Crack

Pictured

Time Domain Imaging (TDI)™
Utilizes an echo (amplitude & polarity) arrival ‘time’ as a reference, such as standard A-Scan, B-Scan and C-Mode type images.

PBGA Popcorn Crack

PBGA Popcorn Crack - Application Note 245

PBGA Popcorn Cracks
Acoustic image of PBGA left, optical image middle, diagram right

Sample & Method

This Plastic-packaged Ball Grid Array (PBGA) was imaged from the top side. Gating of the return echoes was at the interface between the molding compound and substrate.

Result

The large red area is a “popcorn crack” originating beneath the die. Popcorn cracks result when retained moisture expands during heating such as reflow. In addition, numerous small delaminations (red along the vertical and horizontal metallization lines) exist between the molding compound and the substrate metallization. Delaminations such as these would permit outside contaminants to travel toward the die. Some of the delaminations extend from the edge of the package to the area of the popcorn crack.