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placing double sided pcb on a heat sink

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aliyesami

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i am looking for a way to place the pcb on a heat sink and electrically isolate it , what are my options? i am looking at thermal pads but i dont know if they completely will isolate the pcb electrically from the heat sink .
are there any sprays available that i can use?
 

SunnySkyguy

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There is a wide range of thermal elastomers.

What are your specs for Area, Watts, Volts and thermal resistance?

note that some require high pressure to realize low Rth.
 

aliyesami

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my area is 7X11 inches , the voltage will be 45 volts , total wattage 300watts .
I don't know what the thermal resistance is . i just need to fully isolate the pcb nets and vias on bottom side from the heat sink I am not worried about the heat as pcb will not be producing any heat .
 

SunnySkyguy

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So this is just an adhesive problem? What about blocking convection flow of the air to heatsink with an epoxy board which is an insulator?

Got any pictures?
 

aliyesami

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no its not an adhesive problem but rather isolation problem , if i cant glue the pcb to the heat sink i can always screw it down but what is important for me is to isolate the base of pcb from heat sink conductive surface.
I am not worried about the convection flow , i am worried about electrical
short circuiting of the pcb tracks on the lower sider touching the heat sink.
 
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SunnySkyguy

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If you are worried about sharp protrusions then a rigid insulative tape or a larger gap is needed, otherwise any double sided tape 1-2 mm should work, with 1-5 kV/mm
 

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I think you are looking for some insulating film like this:
https://www.aavid.com/product-group/interface/films-insulating

There are other types that are thicker, but have much worse thermal conductivity.

- - - Updated - - -

The previous stuff looks like it doesn't come in sheets (though I know a place I worked at before used similar stuff on our heatsinks). This might be a fit for what you want it has adhesive and comes in 8" x 8" sheets.
https://www.aavid.com/product-group/attachments/tape
 

FvM

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Plastic stand-offs and screws would be the standard option.
 

aliyesami

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The previous stuff looks like it doesn't come in sheets (though I know a place I worked at before used similar stuff on our heatsinks). This might be a fit for what you want it has adhesive and comes in 8" x 8" sheets.
https://www.aavid.com/product-group/attachments/tape

yes this is what i want, where can i buy it ? on their website they are not selling .

thanks
 

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