BGAs are susceptible to damage from thermal-mechanical warpage stresses as well as mechanical bending stress.

BGA damage 1

The damage tends to be subtle and isn’t visible at low magnifications such as the image above of a microsectioned device.

BGA damage 2

At higher magnification a fracture became apparent in the upper layers of the die.

BGA damage 3

In the image above, the die attachment appears to have failed and there is a void in the molding compound due to a processing flaw at molding.

BGA damage 4

The bottom of the die separated from the molding compound and a fracture radiates away through the molding compound.

BGA damage 5

However, the PWB laminate under the BGA pads also showed fractures suggesting that the assembled PCBA was bent out of plane. It doesn’t take a great deal of bending to induce this type of damage, so the problem may not be apparent at the moment it is caused.

Check out SEM Lab, Inc.  to learn more.

ceramic capacitor 1

This is an optical image of the capacitor showing the part number.

ceramic capacitor 2

This is the section after final polish. Note the lack of a solder fillet between the right side termination and the lead.

ceramic capacitor 3

This is a BSE SEM image of the section. These anomalies are parallel in the plane of the capacitor plates (i.e. knit line defects) raising a question about the “as-sintered” strength of the structure.

ceramic capacitor 4

This fracture shows characteristics of thermal shock damage, possibly during attachment of the device leads to the capacitor end caps.

ceramic capacitor 5

This fracture traverses capacitor plates of opposite polarity, which typically results in a shorted capacitor. The fracture appears to propagate from a knit line defect suggesting the root cause is related to the original firing of the multilayer ceramic element.

Check out SEM Lab, Inc.  to learn more.