Solder joints on heat sinks matter?

[jm1234]

Hi,
solder joints on heat sinks - how much do they matter? Could poor joints on heat sink cause issues if they are not properly joining to hot ground?
I'm looking at power source module of Panasonic plasma TV and I see many of these having visually poor quality, but could they matter? In general I would guess no, but I saw a video where someone was stressing out the importance of tightening the screws when fastening the power source board specifically for the ground to be connected properly.
Thanks

[stj]

if a heatsink has more than one mounting screw/pin/tab then you need to check if they are used - sometimes the heatsink is used to bridge 2 tracks across a board.

[CapLeaker]

Usually if a transistor is mounted to a heat sink, I mount it on the heat sink first, then I solder the transistor to the board. Reasoning is that the solder joints are not being stressed. Some transistors will actually pop their lid off if you solder them first and then mount it.

[stj]

if a heatsink has more than one mounting screw/pin/tab then you need to check if they are used - sometimes the heatsink is used to bridge 2 tracks across a board.

[momaka]

if a heatsink has more than one mounting screw/pin/tab then you need to check if they are used - sometimes the heatsink is used to bridge 2 tracks across a board.

+1

It depends on the PSU / board manufacturer, really.
Some indeed use heatsinks to bridge/route ground to various places on the board, while others don't and the solder spots that hold down the heatsink(s) are isolated from the rest of the circuit. In any case, it's good to re-solder them if they are cracked. Otherwise, vibration can make the whole heatsink move more, eventually causing solder joint fractures to the parts attached to the heatsink... or in very severe cases, leads pulled out of parts.