veggies Posted June 22, 2016 Share Posted June 22, 2016 I just got my replacement control board in the mail and have already removed the original. The replacement process seems super easy, but I wanted to check first - what's the deal with the thermal paste? I can salvage the paste from the old board and reuse most of it, but would like confirmation that I’m ok without wiping everything super clean and getting new paste all over. I googled around but didn't see much beyond a brief mention in a youtube video. Thanks. Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted June 22, 2016 Share Posted June 22, 2016 While you have it apart, maybe check to see if the wheel spins freely with no resistance. Is the tire installed correctly? I wonder if there could be some contact between the tire and the shell somewhere. When you installed the tire, after you put it all back together, was it spinning freely? I'd hate to see you go through all the work of replacing the board and then have the same problem happen again if it's due to something physically interfering with the wheel or a short somewhere in the motor harness perhaps. Regarding the paste, I think it's usually better to remove the old paste, clean things with some Goo Gone, and then reapply a new layer of paste as it acts as a heat transfer medium. With CPU heatsinks they always recommend new paste, but I don't know if it's that critical with these EUC's. I figure if you've got it all apart, one more step isn't a huge deal. I think the main reason is to minimize air bubbles being trapped when you use new paste versus sandwiching the old paste back together. Link to comment Share on other sites More sharing options...
esaj Posted June 22, 2016 Share Posted June 22, 2016 6 hours ago, veggies said: I just got my replacement control board in the mail and have already removed the original. The replacement process seems super easy, but I wanted to check first - what's the deal with the thermal paste? I can salvage the paste from the old board and reuse most of it, but would like confirmation that I’m ok without wiping everything super clean and getting new paste all over. I googled around but didn't see much beyond a brief mention in a youtube video. Thanks. Where exactly is this paste? Doesn't the mainboard come as one "block" that you just put in place and attach the wires again? If you're talking about the thermal tape/pads/whatever between the mosfets and the heatsink, you can't use just any paste; most "normal" thermal paste is electrically conductive, and the mosfet metal-parts must be electrically insulated from the heatsink, otherwise you short the drains of the high- and low-sides of the bridges together! Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted June 22, 2016 Share Posted June 22, 2016 At 4:20 in the video there is paste discussed between the control board heatsink and the heat dissapator plate. I've never replaced a Ninebot control board, but I'm betting they wouldn't make an end user attach mosfets onto the heatsink block? Link to comment Share on other sites More sharing options...
dmethvin Posted June 22, 2016 Share Posted June 22, 2016 @veggies I think @HunkaHunkaBurningLove covered most of it. If you got the board assembly you just need to clean and replace the compound between the board heat sink and the backing plate that is open to the wheel well. I tend to put a thin coat on both surfaces with something like a razor blade, making it slightly thicker in the center. That way you are less likely to trap air bubbles. (Imagine the worst case where you just put an "O" of compound around the outside of the heat sink, there would be a large air pocket in the center!) In the video you can see they were super generous with the compound at the factory so it's not a big problem if you use a little too much. You can scrape off the excess from the edges if you want. Generally it is viscous enough that it won't go anywhere if you leave it there. Link to comment Share on other sites More sharing options...
veggies Posted June 22, 2016 Author Share Posted June 22, 2016 The control board has a metal block (heatsink, I believe) which attaches to a large, flat metal plate. The plate goes onto the rubber grommet and white plastic. The control board, with its metal block, goes onto the plate. If this is confusing I'd check out this video, which shows the paste I'm talking about. It's thermal paste - if you've ever assembled a desktop computer, this is the same stuff that you use to bond a CPU to its socket. Also I checked with Jake at forwardca and he said to just salvage as much paste as possible and carry on with the procedure, so... fingers crossed. I'm all done now, just waiting for the verification from ninebot which will green-light my unit for driving. Link to comment Share on other sites More sharing options...
esaj Posted June 22, 2016 Share Posted June 22, 2016 21 minutes ago, veggies said: The control board has a metal block (heatsink, I believe) which attaches to a large, flat metal plate. The plate goes onto the rubber grommet and white plastic. The control board, with its metal block, goes onto the plate. If this is confusing I'd check out this video, which shows the paste I'm talking about. It's thermal paste - if you've ever assembled a desktop computer, this is the same stuff that you use to bond a CPU to its socket. Also I checked with Jake at forwardca and he said to just salvage as much paste as possible and carry on with the procedure, so... fingers crossed. I'm all done now, just waiting for the verification from ninebot which will green-light my unit for driving. Yeah, it's probably the basic silicon paste. My bad, I didn't watch the video first, so I was wondering whether they actually make you attach the mainboard mosfets to the heatsink yourself In which case silicon paste would be a disaster... I use the stuff for TO-220 heatsinks all the time: But in these cases the electrical conductivity of the paste doesn't matter, because the heatsinks aren't touching anything, it's a bit different with the wheel halfbridges... Link to comment Share on other sites More sharing options...
Chriull Posted June 22, 2016 Share Posted June 22, 2016 1 hour ago, veggies said: The control board has a metal block (heatsink, I believe) which attaches to a large, flat metal plate. The plate goes onto the rubber grommet and white plastic. The control board, with its metal block, goes onto the plate. If this is confusing I'd check out this video, which shows the paste I'm talking about. It's thermal paste - if you've ever assembled a desktop computer, this is the same stuff that you use to bond a CPU to its socket. Also I checked with Jake at forwardca and he said to just salvage as much paste as possible and carry on with the procedure, so... fingers crossed. I'm all done now, just waiting for the verification from ninebot which will green-light my unit for driving. Normally thermal paste is not used for bonding. Especially not for a CPU to its socket ;). The thermal paste is to minimize air between two metal parts and (always?) has a higher thermal resistance then the metal but much lower than air. The metal is never real flat - there is always some roughness which should be filled with as little as possible paste. It should just flatten out the roughness of the metal. So normal heatsinks are fixed to the Mosfet (CPU or whatever) so that some mechanical pressure holds them together (like the screw in @esaj's foto) and one should use as little of the thermal paste as needed! Since with the ninebot the thermal paste is used for "glueing/bonding" still you should try to use as little as possible so that it still holds the heatsinks together. If "as much paste as possible" is used and a thicker film of paste is between the heatsinks cooling could be worsened. It was not to be seen in detail, but in speedyfeets video after 4:47 it seems that there are screw holes in the heatsink which maybe could be used to really fix the aluminium plate to the heatsink? If so, together with just a minimal film of paste screwing the heatsinks together could greatly reduce the thermal resistance and so improve cooling! PS.: thermal Paste has more than 20 times worse thermoconductivity (0,8..10 W/mK) as aluminium (236 W/mK). Air has just 0,0262 W/mK Link to comment Share on other sites More sharing options...
esaj Posted June 22, 2016 Share Posted June 22, 2016 17 minutes ago, Chriull said: So normal heatsinks are fixed to the Mosfet (CPU or whatever) so that some mechanical pressure holds them together (like the screw in @esaj's foto) and one should use as little of the thermal paste as needed! Yup, there's just a very thin film of the paste between the heatsink and the component, I have 5ml (milliliter) syringe of the stuff, and I've used it in dozens of those heatsinks... probably used like 1/3rd of it. I smear a very thin film on the back of the component, then put the screw on and twist it about as tight as I can, at which point some of the paste already comes out from the sides (like seen in the picture, if you look at the "edge" between the component and the black heatsink). The idea is to fill very small cavities and "air pockets" between, but leave as much metal-to-metal -connection as possible (in cases where it won't matter that the component and the heatsink are electrically connected). I've also got some heat pads in case I need to insulate the component electrically from the heatsink, but haven't needed them so far. Link to comment Share on other sites More sharing options...
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