Will TO220 FET legs get disconnected from the silicon?

[treez]

Hi,
We have left our 60W Offline Flyback SMPS running for the weekend at 20W. I have just remembered that I forgot to solder the FET heatsink pin to the PCB. ..The TO220 FET hangs upside down in the enclosure, therefore, the heatsink will be weighing down on the legs of the TO220 FET which are soldered into the PCB…….do you think the FET legs may disconnect from the silicon inside the TO220 package, due to the weight of the heatsink? The heatsink is part number SK 469 35 STS BY Fischer.com…..

TO220 Heatsink (SK 469 35 STS)
https://www.fischerelektronik.de/we...ded heatsinks for PCB mounting/VA/SK46935STS/

 

[dick_freebird]

I would expect that if there were a thermal problem, the
solder joints holding the FET+HS assembly to the board
would be the first to let go. Liquidus of solder is well below
any of the other critical temperatures.

Of course once the first leg loses electrical connection,
other badness might ensue (such as, lose the source leg,
immediate gate rupture as the D-B(S) junction is what
shields the D-G thin oxide); lose G, expect uncontrolled
D-S conduction / dissipation.

Plenty of ways to kill a die short of lifting leads or bond wires.