Hi, I would like some opinions on reusing a Heatsink. It's for an Amplifier Board using 6 pairs of output transistors. The transistors are soldered to the PCB, then fixed to heatsink in 2 parralel lines, P and N fets on opposite sides of board. The problem I'm facing is, I have two tasty heatsinks I would like to use but they were salvaged from another project and have several 3mm holes drilled in it already, which would clash with the spacing of the transistors I need to fix to it. I was thinking of getting a aluminium plate made to fit on top of heatsink to give me a new unblemished surface to work with. If I then drilled through this plate and mounted transistors to it, there are a couple of places where the transistors although mounted on the new unblemished surface, underneath it on the heatsink proper, there would be a couple of transistors that would be on top of previous 3mm holes. I have read something about possible hot spots when mounting transistors and wondering if this could be the case with my proposed idea, or whether the Aluminium plate would still dissipate the heat effectively? If your opinion is that this is workable, would you suggest a thin skin type plate say 1mm, or something more substantial 3, 4, 5mm. I would probably look to secure plate sandwich fashion, with Transistor mounting bolt going through plate in to heatsink proper and also supplement these with extra screws through top plate into heatsink to maintain good thermal contact. Apologies for such a wordy submission, but thought necessary so you get the full picture.
Hi, OldDIUthanks for your replies. I would prefer not to have flying leads from PCB as things would get messy. The transistors mount under the board with the legs pointing out to edge of board.
HI analog. You're saying having a couple of 3 mm holes underneath plate and possibly what would amount to underneath transistor tab would be OK? What do you think about thickness? Torn between thin for more intimate contact with heatsink or think to spread heat more evenly into plate to mitigate the 3mm hole in heatsink at the expense of possibly reducing thermal transmission from transistors to heatsink.
HI analog. You're saying having a couple of 3 mm holes underneath plate and possibly what would amount to underneath transistor tab would be OK? What do you think about thickness? Torn between thin for more intimate contact with heatsink or think to spread heat more evenly into plate to mitigate the 3mm hole in heatsink at the expense of possibly reducing thermal transmission from transistors to heatsink.
Attempting to clarify previous post.
What do you think about thickness of top plate? I'm torn between thin for more intimate contact with heatsink from transistor base or thick to dissipate more heat into top plate before dissipating into heatsink in order to compensate for the voids caused by 3mm holes underneath plate. Possibly at the expense of reducing direct thermal transmission from transistors to heatsink.
What do you think about thickness of top plate? I'm torn between thin for more intimate contact with heatsink from transistor base or thick to dissipate more heat into top plate before dissipating into heatsink in order to compensate for the voids caused by 3mm holes underneath plate. Possibly at the expense of reducing direct thermal transmission from transistors to heatsink.