Is there a Quark 125B thermal problem?

[zeropointbug]

Hi,

I am hearing that people at having over heating problems with the Quark 125B?!
Are the transistors not making good contact with the aluminum case or something? I WAS planning to lap the bottom of the Quark and use Arctic Silver paste and mount it to the upper aluminum chassis for very cool running.

I hope this isn't true since i just got my 125B yesterday, and a 540C 7XL.

ANY and ALL issues, comments on the subject are appreciated.

Zeropointbug

[neweuser]

Originally Posted by zeropointbug

Hi,

I am hearing that people at having over heating problems with the Quark 125B?!
Are the transistors not making good contact with the aluminum case or something? I WAS planning to lap the bottom of the Quark and use Arctic Silver paste and mount it to the upper aluminum chassis for very cool running.

I hope this isn't true since i just got my 125B yesterday, and a 540C 7XL.

ANY and ALL issues, comments on the subject are appreciated.

Zeropointbug

The Quark does have heat issues. But with proper cooling you should be fine. If you look on the store, there is a heatsink that is sold for this application.

[zeropointbug]

I wonder if lapping/sanding the bottom of the Quark with 600 fine sand paper and using Arctic Silver and pressing it to a thick aluminum upper chassis brace that would take all heat away.

[neweuser]

Originally Posted by zeropointbug

I wonder if lapping/sanding the bottom of the Quark with 600 fine sand paper and using Arctic Silver and pressing it to a thick aluminum upper chassis brace that would take all heat away.

I would get the heat sink and not sand the bottom of the Quark. Then use the arctic silver to attatch the heatsink.:027:
you could however drill holes in the heat sink as well. I think this is what Mike did to his.

[zeropointbug]

You don't have to lap the bottom, it would just increase the heat dissipation (not by much though). That Arctic Silver is some THICK stuff though, i've done quite a few CPU heat sinks and just a membrane of the stuff is enough... well i shouldn't say that, THE THINNER THE BETTER, PERIOD.

[BrianG]

The heat problem with the Quarks is two-fold really.

1: The case doesn't have enough thermal mass or fins to effectively pull the heat away from the FETs and dissipate it. This is where an added heatsink comes in. Even though the ESC doesn't have a beefy enough heatsink out of the box, at least Quark provided a nice spot to attach one!

2: The construction is a bit wacky, but for a reason. There is an Aluminum slab between the FETs and the case. This slab is held to the case via some type of soft rubbery thermal pad. The same material is use between the FETs and the slab. So there are three layers of material between the FETs and the casing; FETs -> thermal pad -> slab -> thermal pad -> case. So thermal transfer isn't the best right out of the box. The slab is really just a spacer so the caps on the end will sit right.

I'm sure the ESC would run OK like this since that is how it was designed - but after some use and dirt working its way into the case, the adhesive on the thermal pad becomes somewhat unstuck. Of course this drastically affects heat transfer.

What I did was pull the ESC apart (be careful of the SM cap by the button!), and remove the ESC circuit from the case and remove the rubber stuff on both sides of the slab. Because the rubber stuff is fairly thick (about 1/2mm), a new thicker slab needs to be made. The existing one is about 2mm thick so, a 3mm (1/8") thick piece of aluminum works great. Once cut to the right size and polished, and apply thermal epoxy to secure the FETs to the slab, and then epoxy the ESC/slab to the casing. Just be careful not to get the Arctic Silver stuff on the FET leads, unless you use the non conductive version.

Once the epoxy cures, you'll notice a huge difference in the thermal properties of the ESC. It will heat up faster and cool off faster. It will also feel hotter to the touch when running. These are all good things because it means the heat is not staying IN the ESC. Add a heatsink to get rid of that heat and you are golden.

Of course, this almost definitely VOIDS THE WARRANTY, so be advised.

[neweuser]

Originally Posted by BrianG

The heat problem with the Quarks is two-fold really.

1: The case doesn't have enough thermal mass or fins to effectively pull the heat away from the FETs and dissipate it. This is where an added heatsink comes in. Even though the ESC doesn't have a beefy enough heatsink out of the box, at least Quark provided a nice spot to attach one!

2: The construction is a bit wacky, but for a reason. There is an Aluminum slab between the FETs and the case. This slab is held to the case via some type of soft rubbery thermal pad. The same material is use between the FETs and the slab. So there are three layers of material between the FETs and the casing; FETs -> thermal pad -> slab -> thermal pad -> case. So thermal transfer isn't the best right out of the box. The slab is really just a spacer so the caps on the end will sit right.

I'm sure the ESC would run OK like this since that is how it was designed - but after some use and dirt working its way into the case, the adhesive on the thermal pad becomes somewhat unstuck. Of course this drastically affects heat transfer.

What I did was pull the ESC apart (be careful of the SM cap by the button!), and remove the ESC circuit from the case and remove the rubber stuff on both sides of the slab. Because the rubber stuff is fairly thick (about 1/2mm), a new thicker slab needs to be made. The existing one is about 2mm thick so, a 3mm (1/8") thick piece of aluminum works great. Once cut to the right size and polished, and apply thermal epoxy to secure the FETs to the slab, and then epoxy the ESC/slab to the casing. Just be careful not to get the Arctic Silver stuff on the FET leads, unless you use the non conductive version.

Once the epoxy cures, you'll notice a huge difference in the thermal properties of the ESC. It will heat up faster and cool off faster. It will also feel hotter to the touch when running. These are all good things because it means the heat is not staying IN the ESC. Add a heatsink to get rid of that heat and you are golden.

Of course, this almost definitely VOIDS THE WARRANTY, so be advised.

You wouldn
t happen to have pics of this process would you? LOL

[BrianG]

Sorry, no pics. It's pretty easy to do really.

Care to donate your Quark for picture-taking purposes? ;)

I forgot to mention that once you do this, it's not coming apart without something breaking. You might be able to seperate the slab/ESC from the case, but that's about it. I know of no solvent that will dissolve thermal epoxy without damaging anything else in the process.

[neweuser]

Originally Posted by BrianG

Sorry, no pics. It's pretty easy to do really.

Care to donate your Quark for picture-taking purposes? ;)

I forgot to mention that once you do this, it's not coming apart without something breaking. You might be able to seperate the slab/ESC from the case, but that's about it. I know of no solvent that will dissolve thermal epoxy without damaging anything else in the process.

I've been contemplating on donating it period! LOL
I think, this would be the reason they use pads, so that they can take them apart to work on. I thought about this a long time on how to do it better. Mine really does not get that hot though right now. Mainly for me, it's the start and stop thing that I'm working on getting resolved right now.
But basically, if I take it apart, I will need two slabs of 1/8th" of amluminum to replace the pads right? I already have thermal epoxy that is Arctic silver. Not sure if it's non conductive though, will this matter?

Here is a thread with more on the subject a long with some pictures http://www.rc-monster.com/forum/showthread.php?t=3861. I have done something similar to BrianG with my Quark. Since I have modified my ESC I have been really happy with it's performance. It has not thermaled since its been modified. I don't even use a fan on my esc, 1/8 buggy for 25 minute runs.

BrianG used a 3mm slab of aluminum between the FETs and the case and then it has the perfect spacing. That way is easier then the way I did mine. It really is easy to do. The hardest thing to do is open the case!

I just ordered another Quark for a CRT project, I'm sure I will modify it as well.

[zeropointbug]

Hmmm, maybe the aluminum slab is for durability reasons maybe? Instead of having the FET's right up at the case...

I also checked the FET, from what i can see the FET's are Infineon made, and are rated at 30V, and 100A capability each... thats the page i found anyways.

I wonder when ESC makers will utilize heat pipes to dissipate the heat, VERY effective, and makes for a lot of options as far as setup.

Do you think i will be okay with running 5s2p A123 cells with a 7.5 lb 1/8 emaxx buggy conversion, as far as thermals go?

[zeropointbug]

Now wait, i found another page that says 50A. And 2.2mOhm, and it looks like them too.

They are called "OptiMOS 2 power transistor"

They drain at 50A even at 100 degrees celcius, and 200A pulse at 25 degrees

Power dissipation is rated at 104watts, wow.

[BrianG]

Neweuser: Well, you can donate it me if you'd like. :) If you do what I did, you will only need one 3mm thick slab. Regular AS adhesive has some capacitive properties and might cause problems if it drips onto the legs of the FETs (especially the gate lead). AS has another type that is non-conductive and non-capacitive. However, I was careful and used the normal stuff and haven't had any problems. I'm sure the use of the padding was somewhat determined by ease of working on it. I know mine is useless for warranty work now, but I personally think it was worth it for the thermal performance compared to what it was before the mod.

zeropointbug: From what I can tell, the slab is more of a spacer. The electrolytic caps on the end of the ESC are a little higher than the tops of the FETs, so the slab takes up some of that space. It probably also acts like a heatspreader to some degree as well.

The datasheet for the FETs can be found here. In this post, I made some observations about these FETs and why they may not like 6s. make sure to look at the derating charts...

[coolhandcountry]

Irun a 80b quark with pretty good sucess. I mounted it flat on the aluminum chassis.

[zeropointbug]

Coolhandcountry What motor and how many cells are you running off the 80B?