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Identifying thermal insulation on a FET

76Capri

May 8, 2012
7
Joined
May 8, 2012
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7
A power supply I am trying to repair had these sleeves on 4 of the FETs. there are other FETs in the supply, but none have these sleeves on them.

The sleeves are damaged and I'm reluctant to reuse them. Is a thermal sheet or paste ok or did the designer of the supply have some sort of intent with these sleeves that i don't know about.

Been searching and have yet to find a place to buy these FET sleeves.

Any help would be appreciated.

7176606020_d40159a2cc_n.jpg


7176606076_4b7a179861_n.jpg


7176606140_a791d7ca80_n.jpg
 

shrtrnd

Jan 15, 2010
3,876
Joined
Jan 15, 2010
Messages
3,876
That looks like a pretty heavy-duty copper buss bar they're mounted on.
The mark on the copper between the devices and the board makes me think the
PCB also had some type of cover over it.
I can't think of a thermal reason for the covers, so my bet is that the shields are just
to keep the environmental elements off the devices, like water or whatever.
(to prevent a short or mostly to prevent corrosion from the elements),
I'm assuming the covers are not electrically conductive?
 

davenn

Moderator
Sep 5, 2009
14,254
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Sep 5, 2009
Messages
14,254
Yes that first link from Harald nice one :)

I'm assuming the covers are not electrically conductive?

shrtrnd, no they are not. I have seen them more and more often over recent years. Particularly in switch mode PSU's and occassionally in audio amps, but more often the ones in Harald's second link are used

Dave
 
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