# Circuit board insulation



## DIYguy (Sep 18, 2008)

Here's a question for all you electrical boyz. I'm scavaging some heat sinks. They have IGBT's mounted to them and the whole surface is covered in the waxy insulation goop. What's the best way to remove this stuff?? 

Thx.

Gary


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## Tesseract (Sep 27, 2008)

Waxy??? That's a new one... Toluene or xylene will safely remove wax from most non-plastic things, but are you sure that's what it is?


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## DIYguy (Sep 18, 2008)

Tesseract said:


> Waxy??? That's a new one... Toluene or xylene will safely remove wax from most non-plastic things, but are you sure that's what it is?


No Im not sure at all. OK, it's definitely not wax. But I can scrape it off with my thumb nail if I press real hard. It's almost like a soft plasticy kindof coating. You can tell that it was dipped in the stuff because there are droplets that formed and solidified. I can't take a pic cause I lost my BB today Well I suppose I could bug my daughter or grab my video camera...but it takes worse still shots than my BB .. . lol


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## Guest (Jan 26, 2009)

White thick greasy stuff is thermal compound to allow transfer of heat. All these things use that stuff. These things need to transfer the generated heat to the sink to keep it alive. It is normal stuff. Maybe IGBT's use a different kind of thermal compound but none the less it is most likely a thermal compound for transfer of heat. That is why they are attached to a heat sink. 

Pete : )


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## DIYguy (Sep 18, 2008)

Hey Pete,.. no, I know what the thermal compound is. This is the insulation coating the entire base of the heatsink and the IGBT's as well. The same stuff is on the circuit board. It's almost clear... but kind of faded yellow in colour.


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## Tesseract (Sep 27, 2008)

DIYguy said:


> Hey Pete,.. no, I know what the thermal compound is. This is the insulation coating the entire base of the heatsink and the IGBT's as well. The same stuff is on the circuit board. It's almost clear... but kind of faded yellow in colour.


Is this by any chance military surplus equipment? Regardless, it sounds like it is either Parylene, in which case you are f'ed, or acrylic conformal coating, which is about the easiest one to remove of them all. 

A good overview of removal techniques is in this PDF: 

http://www.ccrco.com/study.pdf

I use my hot air soldering station to remove parts from acrylic and polyurethane coated boards, but since you need to remove parts from a heat sink (ie - much more thermal mass) you may want to pop the whole assembly into the oven at 200F to loosen them up.


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## DIYguy (Sep 18, 2008)

Thank you.... I'll give it a try and see what works.... 

Gary


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## Wirecutter (Jul 26, 2007)

I think it depends on whether it's insulation or potting compound. I've seen line filter modules (Corcom?) that are potted with this black, rubbery, maybe slightly foamy stuff. It's a real mess, and heat will get it to flow. I've used a propane torch (and some care) to remove that stuff.

If it's potting compound, like for example, what Sevcon uses for their motor controllers, yuck. Get an old crock pot and stick the stuff in there. Fill it up with Dynasolve 711 (web search) and let it cook on low heat outdoors. Now, you said you're scavenging heat sinks, not the IGBTs, right? Good, because hot Dynasolve 711 will dissolve many plastics and epoxies, but not metal. That includes semiconductor packages. With time, the heat can also delaminate PCBs.

-Mark


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## DIYguy (Sep 18, 2008)

Wirecutter said:


> I think it depends on whether it's insulation or potting compound. I've seen line filter modules (Corcom?) that are potted with this black, rubbery, maybe slightly foamy stuff. It's a real mess, and heat will get it to flow. I've used a propane torch (and some care) to remove that stuff.
> 
> If it's potting compound, like for example, what Sevcon uses for their motor controllers, yuck. Get an old crock pot and stick the stuff in there. Fill it up with Dynasolve 711 (web search) and let it cook on low heat outdoors. Now, you said you're scavenging heat sinks, not the IGBTs, right? Good, because hot Dynasolve 711 will dissolve many plastics and epoxies, but not metal. That includes semiconductor packages. With time, the heat can also delaminate PCBs.
> 
> -Mark


Thanks Mark, I don't think it is potting compound. Maybe some kind of urethane. I took a couple pics. Not sure how good they are...
I ended up scraping the majority of it off.


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## Wirecutter (Jul 26, 2007)

I don't know what solvents dissolve urethane, if that's what that is, or how safe they are to use. That looks like ugly stuff you've got there.

I've heard that every good mechanic's tool box includes a dull, non-serrated steak knife with the point broken off. This tool is instrumental in scraping off gaskets and such with minimum damage to the underlying surface. I think I'd try something like that, or perhaps a putty knife with the corners dulled.

-Mark


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## order99 (Sep 8, 2008)

A plain wooden paddle, sanded to a dull 'edge', works wonders and won't scratch any metal harder than lead. One of my favorite Tool-and-Die cleaners...


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## DIYguy (Sep 18, 2008)

order99 said:


> A plain wooden paddle, sanded to a dull 'edge', works wonders and won't scratch any metal harder than lead. One of my favorite Tool-and-Die cleaners...


Thank you all for your help. This forum is really great. 

I have a wood shop in my basement and like to use hard maple a lot. This works great for scrapers like you mention! 

Gary


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