Heat Sink to PCB Bond Defects - Application Note 2299
Sample & Method
A single-sided PC board with a metal heat sink layer bonded to the bottom side.
Bonding of the heat sink element to the board is incomplete, as seen in the numerous red areas, which are delaminations. The gating used here has also captured the attachment of some components to the far side of the board.
The red areas are a concern because they will reduce the heat sink function.