Flip Chip Underfill Multiple Voids - Application Note 2466
Sample & Method
A flip chip assembly, imaged by the 3V module through the overlying silicon die.
The four small white features are voids in the cured underfill. Common defects in the flip chip underfill region are voids, delaminations, cracks and failure of solder bump bonds.
Each of the four voids is in contact with a solder bump. The voids are an empty space into which solder may creep at normal operating temperatures. Solder creep may cause the bump to collapse and the connection to be broken.