PBGA Cross Section Voids

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 Cross Section Voids

PBGA 3D Cross-Sectioned Voids in Molding Compound - Application Note 206

PBGA Cross Section Voids
Acoustic image left, optical image of PGBA middle, diagram right

Sample & Method

The Acoustic Solid shown in Application Note #202 has been sectioned vertically to reveal internal features. Since the Acoustic Solid is a virtual representation of the PBGA, including all internal features, sectioning is nondestructive.

Result

The die (blue) lies at the center of the package near the bottom. To the left and right of the die is the FR4 substrate (also blue). No defects are associated with these features. The molding compound above these features, however, displays numerous yellow items. These are voids in the molding compound. A few of the larger voids are blue.