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Power amplifier heatsinks

Posted: Sat May 04, 2019 1:53 pm
by g8vpg
Does anybody know about the grey coloured, plastic looking film that is often applied to heatsinks? I am led to believe that it is a heat conducting layer that is used in preference to conventional heat sink paste. My QO100 amplifier heatsink has this film applied, but it is clear that the amplifier case is quite a bit warmer than the heatsink and it looks more like an insulating layer to me. Does anyone have any professional knowledge of why and how this is used?
73 Shaun.

Re: Power amplifier heatsinks

Posted: Sat May 04, 2019 2:16 pm
by g0mjw
Sounds like a thermal pad. It will have some thermal resistance so you expect a gradient across it.

E.g. https://uk.farnell.com/3m/120mm-1m-0-5m ... dp/2820143 where you will find a data sheet.

Mike

Re: Power amplifier heatsinks

Posted: Sun May 05, 2019 3:16 pm
by G8GKQ
Hi Shaun

Those thermal pads were standard on the GigaTech PAs and blown heatsinks. Mine was in a bit of a state so I scraped it off and used heatsink compound.

The "Polish PAs" that Noel and I now use also have one. Seems quite effective when properly mounted (>200 W dissapation on mine)

Dave

Re: Power amplifier heatsinks

Posted: Sun May 05, 2019 7:09 pm
by G1BVI
Be careful because it could be an insulator too.
Not seen an image but back in the day 2N3055 devices in a TO3 package had to be insulayed from the heatsink but still im thermal contact using thermal paste
Mica washers were used and other materials.

73

Nick