# Heatsink Thermal pad



## Anaerin (Feb 4, 2009)

jehan12413 said:


> I need to replace the thermal conductive pads between the heatsink and my curtis controllers. Does anyone know where I can get the material. I would prefer a large sheet so I can cut to the appropraite size. Thanks


You're looking for "Thermal Interface Material". Chances are, you were using a "Thermal Pad", something like this: http://www.startech.com/item/HSFPHASECM-Thermal-Pad-Heatsink-Paste-Alternative-Package-of-5.aspx

But a better bet for heat conductivity is a thermal paste. Something from the "Arctic Silver" brand works best, IMHO, and they have differing types, depending on what you capabilities you need, from Ceramique and Alumina, which are electrically isolating, to their adhesive range. Unlike the pads, they are meant to be applied extremely thinly (Less than the thickness of a human hair), to "fill in the gaps" between the heatsink and the heat source, rather than to be the entirety of the bridge.


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## wd9hik (May 7, 2010)

Be careful, some "Thermal Pads" are there for heat conduction AND electrical isolation from the heat sink. The paste just by itself is not enough electrical isolation on a lot of circuits.

Chris
WD9HIK




Anaerin said:


> You're looking for "Thermal Interface Material". Chances are, you were using a "Thermal Pad", something like this: http://www.startech.com/item/HSFPHASECM-Thermal-Pad-Heatsink-Paste-Alternative-Package-of-5.aspx
> 
> But a better bet for heat conductivity is a thermal paste. Something from the "Arctic Silver" brand works best, IMHO, and they have differing types, depending on what you capabilities you need, from Ceramique and Alumina, which are electrically isolating, to their adhesive range. Unlike the pads, they are meant to be applied extremely thinly (Less than the thickness of a human hair), to "fill in the gaps" between the heatsink and the heat source, rather than to be the entirety of the bridge.


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## Anaerin (Feb 4, 2009)

wd9hik said:


> Be careful, some "Thermal Pads" are there for heat conduction AND electrical isolation from the heat sink. The paste just by itself is not enough electrical isolation on a lot of circuits.


As I mentioned specifically, there is isolating thermal paste as well, along with adhesive isolating thermal paste also.


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## jehan12413 (Feb 4, 2010)

The pad I removed was a shiny green on both sides with a weave in the center, possibly fiberglass or kevlar. In addition thermal paste had been applied to both sides. These controllers were originally designed for 36 volts but since I am now up near 200 volts I want to be absolutely certain that I have good electrical isolation. Thanks for the information.


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## ngrimm (Oct 19, 2007)

You've done some neat things to your Curtis controllers. I have no idea where Curtis gets their pad material but it seems like it may be a compromise between heat transfer and mechanical strength to make sure the two aluminum surfaces can't wear thru the material. Otherwise it seems like they could have used a more traditional plastic material for the sake of isolation and thermal transfer. Some will call me crazy but I have used clear overhead projector transparency sheets that are made to be run thru laser printers for similar applications. I'm not saying they would work in this case but with thermal paste they have worked well for me. A couple off topic questions about your Curtis controllers if you don't mind. When I looked at upping the voltage like you have, the two snags I faced were, all the higher voltage capacitors were much larger physically than the original caps and also I couldn't decide how to power the circuit board. Can you share how you handled those issues. Thank you. Norm


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## jehan12413 (Feb 4, 2010)

The capacitors seem to be the hard part to find, the last one I built used 200v 820uf snap in ones from all electronics. The height is right but as usual not the pin spacing, so I spread the pins and staggered them using every other hole. As far as the control board in the past I tapped 30 volts from a few batteries in the main pack, but with the last one I made a simple regulator which mounts directly on the main bus bars on the power board. It works ok but is not very efficient and generates a lot of heat when regulating 200v down to 30v. I plan to redesign in the future but that's near the bottom of my list.


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## jehan12413 (Feb 4, 2010)

Here is a controller with a simple regulator and heatsink. The height is not important since I do not use the original controller case.


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## jehan12413 (Feb 4, 2010)

Here are some pictures of the capacitors.


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