Heat sink glue?

Ok, I know this guy who just built an E-Revo and he really likes to beat on his stuff, you know the type.....:013:

I was out in the front yard marveling at how much further I could jump on BL and the Revo took a gnarly smack on the lid and knocked the heatsink off my MM.

What do you guys suggest? :032:

Thanks,
Cajun

[BrianG]

Well, you can either send it to Castle, or re-epoxy the heatsink back on there. Just make sure to clean the old stuff off the heatsink and the FETs first (and be careful). I use a flat-bladed exacto to scrape off the major stuff, and then use denatured alcohol to clean everything.

Then, get the Artic Silver Arctic Alumina. Do not use the regular AS epoxy as it contains traces of silver, and while it is not supposed to be conductive, it does have some capacitance which could cause problems if any got on the FET leads.

Thanks Brian. I'll see if I can find some. If not, I'll send it back to Castle.

This is NOT what I'm looking for right?

http://www.radioshack.com/product/in...entPage=search

Or can I use that with zip ties?

Cajun, the same thing happened to me. I would mention, at this point, that now might not be a bad time to consider sourcing a larger heatsink. The hard part of replacing the stock heatsink has been done for you.

I any case, the stuff that Serum is talking about (Arctic Alumina) is actually a two part epoxy. I've seen it on ebay. You can find it at most computer shops. The stuff sets in about 5 minutes. If you make a mess of it, don't go making more of a mess trying to wipe up the excess while it is still wet. Before it sets up hard, which actually takes about 8 minutes or so, it will get rubbery. At this stage, you can carefully go around the stuff that you want to remove with an exacto knife and just peel it off. I'd say that at about the three mintute mark, it will get rubbery. Just because around the traces and stuff with that exacto.

That is good stuff, but it's not epoxy. This is what you are looking for...http://cgi.ebay.com/ARCTIC-ALUMINA-P...QQcmdZViewItem

I suppose that you could use zip ties, but the grease actually sets and forms a light bond. If it shifts and breaks the bond, its thermal conductivity properties decrease substantially. It's better to use the epoxy for this application.

[BrianG]

AAngel: Um, I'm not Serum. ;)

Cajun: Like AAngel said, you could use regular thermal compound, but you'd have to make sure it doesn't move around at all. Even though it may seem solid if you try to move it with your fingers, keep in mind the shocks your truck suffers from jump landings, crashes, etc. Any movement makes that stuff not work right after a while. Plus, any dirt will stick to any stuff that squishes out and makes a mess. Thermal epoxy is your best bet to keep the heatsink attached.

If you decide to go with a bigger heatsink, let me offer you some points to ponder: 1) make sure you can still access the screws to remove the circuit from the case. If the heatsink covers these, maybe drilling a hole where the screws go will work. 2) Attaching a larger heatsink increases the risk of something hitting it since some of it may be hanging over the case, which might rip those FETs right off the board. 3) Attaching a larger sink also increase the weight that the FETs have to support, which could cause the situation in point #2.

Brian, well excuuuuusse me!! LOL.

Sorry man.

Brian is right. Just use common sense. BTW, when mine came off, I just put the stock one back on. I don't have any thermal issues with any of mine.

[BrianG]

lol, no problem. I'm sure Serum was more hurt by that than I was. :)

I think I lucked out, most of the adhesive that was on there came away with the heatsink not on the FETs. I'm a little worried about scraping on them, but I'll clean them the best I can. I also tested it and the MM is still working correctly. I didn't run it much, but I checked all the funtions.

I found the Alumina here so I think I'm going to order some tonight.

The idea is for the heatsink to sit on top of the epoxy and not touch the FETs right? You don't want there to be a chance for the heatsink aluminum to conduct electricity across the FETs right? Or is it sfe to just put it on then push the heatsink down into it?

[BrianG]

That's where I got my compound a while back. Good place to deal with and fast shipping. You might even get it by Saturday.

Actually, you DO want the heatsink to touch the FETs somewhat. The epoxy compound should be just thick enough to fill in the microscopic valleys and pits in the surface of the FET and heatsink, and to allow proper adhesion. The heatsink actually contacts the plastic case of the FETs, which is non-electrically-conductive - it's the leads you don't want to short out.

You don't want too much adhesive. It is good, but not nearly the thermal conductor that aluminum is. Just a thin layer and having the sink touch the FETs is what you want, I would think.

Thanks for the advice guys. The epoxy should be on it's way tomorrow.

I also ordered some of this, looked kind of interesting. I'm going to rework my wiring harness and thought it might help tidy up.

[bdebde]

I use the same stuff; for the smaller wires anyway

[BrianG]

I have mixed feelings about that sleeving. One one hand, it does do a nice job of gathering the wires, but when it gets dirty, it's a PITA to clean. An air compressor is the best bet for that.

That stuff does work good though. Just use heatshrink on the ends to keep them from fraying.