I used to be big into overclocking computers. I am onto better things now. But when I was, tried just about every thermal grease known on the planet. Try this stuff if you haven’t already. http://www.coollaboratory.com/en/products/liquid-pro/
It’s all I used on video cards, cpus in the end… It’s all the same stuff but this actually works in heavy overclocks and holds up over time if you can find a way to bolt it down. Adhesive, I only used to use artic silver artic alumina parts a and b.
Anyways hope that helps. I had extensive experience in computer modding and using the diamond pastes, and all the gimmicks in tim you could find… Made my own sinks. But really tried them all. That stuff is real. The rice grain method is still the best way to insure no bubbles under the sinks too. I saw a vid old lumens did on a light where he still spreads it That’s really old school and doesn’t work too well. I can link a video here with proof. That coolabs needs pre prep though where you rub it into the surfaces premount and it has trouble coming apart on aluminum after it cures. But it works so well, practically soldered, and by the time you want to take things apart it’s time to replace it anyway.
And unlike an overclocked CPU with ~200 watts to deal with in a tiny 1x1cm die, in a flashlight there's no measurable difference in output or runtime or efficiency or anything else that can be measured when comparing the best thermal paste against cheap white silicon-based paste.
That coollab stuff sounds interesting. What's the rice grain method?
My main problem lately though is getting a pill or shelf for the MCPCB that is actually flat. You really need that first I would assume before using something like this grease.
Presumptively, the rice grain method is to use a small bead of the thermal paste about the size of a grain of rice, in the center of the application. Then bolt the device down on top of this allowing pressure to squeeze the paste into a very thin layer. No bubbles. Am I right?
CC - I hear you, and recall that published test on the toothpaste vs. AS5 results (), but, if it's true, this stuff isn't rated at 10% or 50% better than AS5, it's rated 9 to 150 times better (their spec), close to using solder. For me, I'd like to get solder level results for something that can be easily taken apart - this is all wish-list right now, because I still would have to start with a flat surface, and maybe it will never be achievable without re-building the pill of any of these flashlights anyway - seems like the $100 (or more?) lights aren't much better than the $10 lights. Maybe the under $10 lights are the best, because with hollow pills, I would be forced to plug in a copper shelf anyway....
So frustrating... I'm hearing it again from vendors/manufacturers that the parts are made well enough to handle the stock demands and expectations... Ugh.
The higher the heat load that has to be shifted and the smaller the area that heat has to be transferred through, the more improvement you will see with better thermal paste.
Can you measure a difference in light output under any conditions when testing an excellent paste against a crappy paste, assuming the same prep work?
Me? I got AS5, Fujik, GC Extreme for example but not worth it for me - no time. Really needs hours/days to see how they perform after a few cycles of cells for example. Some will hold up better. You can't just do a fresh test, though it's worth something. I thought someone else did and publshed this all before? The toothpaste test? Thought it was all for naught? But I don't think they included coollab - dunno where the thread/results are anymore...
Even if I were to do it, I'd need a perfectly flat pill, I mean perfect... Not sure I can guarantee that on anything I have.
But we're talking about, what, a max of 35 watts for one XML2 before the bond wires fail? And usually at that level it'll be on a 20mm board? That's a huge area and not very much heat, compared to a test designed to replicate a CPU heatsink scenario. The differences between a good paste and a not-good paste will be small enough at our power/heat levels that they will not show up in the amount of light output. Is that not what matters?
In the CPU world, back when CPUs had a tiny exposed die, quality of the paste and the clamp loads present were ultra-critical. That's when most of the thermal paste shootout comparisons were done. Currently, with nearly everything having a bonded-on heatspreader on top though, the performance of the paste is much less critical, the critical joint has moved inside the CPU between the die and the heatspreader where (most times) you can't get at it, and Intel/AMD use very good quality pastes inside there. Some heatspreaders are even soldered to the die.
And in the other thread where I asked about taking a star-pill contact print when using screws, the reason is that there are only two very small areas around the screws where the clamp load is high enough to transfer dye from one piece to the other. It's pretty horrible, really. And thermal pastes only work when the clamp loads are high enough to transfer the dye, anywhere else the layer is too thick to transfer any meaningful amount of heat, and the paste just acts as an insulator instead. And yet... it still works. There's very little if any difference between using screws where there is only a tiny contact area due to MCPCB distortion, and soldered where there is 100% contact. At the levels possible in a flashlight these minutiae just do not make the slightest bit of difference. If they did, if the difference between a good paste and a shitty paste actually showed up at flashlight power/heat levels, I'd be all for it. I'm not for stuff that doesn't make any difference.
Well, sounds like the screws is better than no screws on an aluminum pill? Again, I wish I had all the machining tools, jigs and skills, but I don't now. I've done some soldered MCPCB's, and I'll probably do more, but it's gotta be the right setup for me - I don't have the options you do.
I'm thinking I've seen improvements with screws vs. no screws, specially on zoomies, but I'll try to leverage soldering more, specially on high amp lights.
I’ve wondered why we use paste at all. Especially if someone goes to the trouble to lap both components, how can it really help to put an insulation layer between em? Fujik, especially, as it seems to me to just be a sheet of rubber between 2 pieces of metal.
I use thermal paste or thermal adhesive, because it’s what I’ve been taught to do as a trained chimp. Don’t understand it, just do it.
First time I'm hearing it's an insulation layer. So, a star sitting on it's edges over a hollow pill is better than a star sitting on a solid pill top with AS5 in-between? I'd say prove it - make a believer out of me, because I'm not sure how this makes any sense. I don't have time or the instruments to do the proper measurements. I thought I understood the theory of why to use thermal grease, and I thought I saw measurments that show thermal grease is better than air - I'll believe it until someone proves otherwise.
Whats the purpose of off thermal paste? There is no such thing as two surfaces that have 100% surface contact. It does not matter how highly lapped together two surfaces are there will always be microscopic pits etc. The purpose of the thermal paste is to fill these voids. Nothing else. The same goes for gasket goo.
And if that’s the case, then a microscopic layer is all that’s needed…and of course the better that material carries heat the more effective it will be, right? So Fujik, white silicone, rubber, as it were. A 1/16” thick layer of the stuff like comes on so many lights from the factory, seems exactly like the silicone pad we have on the table to PROTECT the table from the heat of a pot fresh off the stove. It doesn’t allow heat through, but insulates against it…right? Same goes for our Silicone oven mitts. Grab a 425º aluminum cookie sheet out of the oven and not get burned…because the Silicone does not flow heat through, but insulates! Exactly like the silicone insulation on our top end wires.
Thermal paste, yeah, I can see if it’s applied properly that it would fill those microscopic voids. But it’s not to be used like glue or mortar. I guess then that our radiant stove tops are horribly inefficient, glass to metal pan with no paste between them. Point being, for the relatively low wattage of our lights, is it really a big deal?
Place a copper disc 1/2 on 1/2 off a burner, holding the part that isn’t on the burner. Think you’re gonna hold it for very long? And that, with no paste and nothing holding it tight against the hot burner. Heat is going to transfer, microscopic pores or not. Filling microscopic pores might indeed make a difference in an extreme instance, but is it really necessary for us?
That’s my question. If a bare copper star is pressed firmly against an aluminum pill, no paste whatsoever, will it kill anything? Will the difference be measurable? I’m not arguing for or against, just trying to learn something. Sure seems to me the difference is very thin.
From a practical standpoint, if the reflector and lens fit the light properly then the star is going to be pressed firmly against the heat sink of the pill. The only way I can see it making a huge difference to have no thermal paste is if it’s loose, allowing the star to not make contact. Screw it down and it seems to me it’d make little difference. I say that again not in argument, but in lack of understanding.
The efficiency of the led is directly related to how well it gets rid of heat. Theres plenty of graphs around showing this. The holes or microscopic holes are filled with thermal paste to assist in the heat transfer how ever good or bad the surfaces are. If there is an air gap heat is not transferred efficiently. The past takes away this air gap. Ideally the led will have star to pill contact as much as practical with the thermal paste providing a path for anywhere there will be air. When applying thermal paste it pays to put a small dollop in the centre of the star or pill and the two items pressed together so the paste is squeezed from the centre outwards to eliminate any air pockets that may form.
I keep all thermal paste away from my table and stove as I believe it may well be toxic.
I guess what puzzles me is the over use of these fillers. I would think pure metal to metal contact would have optimum results. If microscopically the surfaces are made up of ridges and valleys, then the paste should theoretically fill the valleys while allowing the ridges to make direct contact. With the paste having less ability to transfer heat than the actual metal, these valleys would be the weakness in the thermal pathway.
So, if too much paste is used, there is NO direct metal contact and a considerably weakened thermal path would be the result. Would this seem logical? I guess I’m trying to figure out the best way to use the least amount of paste possible.
The coollab stuff is 100% metal btw - 100% liquid metal alloy.
Metal to metal with very thin grease to fill the microscopic voids, but that's all in the ideal world with perfectly flat surfaces. I can't seem to find a flashlight with a flat pill top, so, for the bigger gaps, what do you do? Is the grease better than nothing? I would think so...
I'm thinking my sanding is only optimizing the pts of contact, but I still think that's an improvement. I've given up hope that the full surface of a MCPCB will contact. Soldering down the MCPCB of course eliminates this issue, if you have that option.
Sorry, thought it went along with the build to some degree.
Thanks for the info on that specialty stuff.
I’ve used a liquid solder from Radio Shack that seems to be a form of graphite. Very thin coming out of the tube, black liquid, that sets up pretty quickly and makes an electrical connection. I wonder how it would perform as a thermal paste? It’s really thin, but acts almost like a glue when set up. This would maintain continuity to the light, if nothing else, if that’s desired.
…and now we return you to the previously scheduled program already in progress.
I dunno if I'd buy this coollab stuff - dunno the cost, but it may be perfect for some applications: knowing you have a flat surface on aluminum, or don't want to reflow the MCPCB. If there were some unevenness like this Y3, hate to waste a lot of it because it sure sounds pricey...
So, the list of poor pill tops for me lately are:
this Y3 (uneven)
XinTD X3 (serious dimple impression in the center)
That’s really old school and doesn’t work too well. I can link a video here with proof. That coolabs needs pre prep though where you rub it into the surfaces premount and it has trouble coming apart on aluminum after it cures. But it works so well, practically soldered, and by the time you want to take things apart it’s time to replace it anyway.
), but, if it's true, this stuff isn't rated at 10% or 50% better than AS5, it's rated 9 to 150 times better (their spec), close to using solder. For me, I'd like to get solder level results for something that can be easily taken apart - this is all wish-list right now, because I still would have to start with a flat surface, and maybe it will never be achievable without re-building the pill of any of these flashlights anyway - seems like the $100 (or more?) lights aren't much better than the $10 lights. Maybe the under $10 lights are the best, because with hollow pills, I would be forced to plug in a copper shelf anyway....
