Heatsink solder fillet

2017/2/2 22:07:26

Opinions. I have a large finned heatsink that we place over a D2pak transistor. This heatsink is designed to heatsink the transistor through the junction of the pad area that the transistor is attached to. The paste pattern we chose was small dots around the outside of the transitor were the heatsink makes contact and a "window pane" of 4 sqaures behind the transitor. Smalls dots were chose to minimize "float/skewing" of the heatsink. Would you expect to see a solder fillet on the heatsink? Would you think it should? Ipc does not address this type of device specifically, but the heatsink maker says minimal 50% solder coverage on the back is required (no fillet).Our inspectors are reluctant to release due to lack of fillet. What do you think?