Our Thermal Epoxy vs Store-bought

hi today I'm going to talk about thermal interface materials [Music] [Music] [Music] first we're going to go through the principles and some of the techniques in using them then we're going to go ahead and cook up a batch of the material and finally I'm going to go ahead and test the material and demonstrate that we can make something here that is superior to what you can buy commercially modern electronic devices produce a lot of heat whether it's a resistor transistors rectifiers laser diodes CPUs and because of modern electronic technology they're very compact this is a 1000 watt transistor so in order to keep these things from overheating you can't depend on just convective cooling you're gonna need to use a heatsink now when you think of a heatsink you think of an extruded piece of aluminum or copper under which you bolt your piece of hardware you mount a fan on but a heatsink in a general sense doesn't have to be an extruded piece of aluminum it's anything that acts as either a heat repository or a heat source to maintain the temperature of your components so it can be liquid cooled it can even be the planet and a geothermal heating and cooling system and the materials involved the metals the metals and the ceramics have a very high thermal conductivity so if we were to bolt this here the heat flow through the components the discrete components is excellent but because there's always going to be a little bit of an air gap the air is an excellent thermal insulator and will interfere with the flow of the heat now typically when you get a heat sink or a piece of material like this the surface is pretty lousy and if you take a look over here at this example I'm going to show you I'm gonna take a heat sink and I'm gonna put a straight edge across it and then turn a light on and if the camera comes down you can take a look and you'll see that there's a fair amount of light in the center of this heat sink and that's because the surface is not flat if we were to bolt a component on to here we would have a fairly large air gap if we were to take a piece of very very high-quality material like this laser mirror and we could fabricate surfaces to this level of optical smoothness and flatness and bolt them together we wouldn't need any thermal interface material at all because the layers become so close together that they're almost atomic to atomic there's no air between them we'll get thermal conductivity through this that's almost equal to the bulk material so if we can make surfaces extremely flat whatever we decide to do with any kind of thermal interface material we will either be able to eliminate it or we will certainly be able to get better performance now if you get a commercial piece of material like this and we want to improve its flatness we can use a technique that has been around for hundreds of years and many amateur telescope makers know about it and it's called walking round the barrel now the reason we use this technique is because by being able to access the surface that we're going to be doing the operation on from 360 degrees we help to reduce any kind of systematic errors that would occur based on the fact that you know we're human beings were not machines now a barrel is a nice surface because it has a good working height it's nice and heavy but if you can't access and I share your bourbon barrel you can in fact get away with an inverted trash bin from Home Depot and if you get ahold of say a piece of wood or a little tabletop to act as a nice working surface and then grab some some frictional glory liners so this is a drawer pad that has a high frictional coefficient and will prevent things from sliding on the surface and then grab a three-dollar commercial mirror commercial mirrors our second surface mirrors the reflection is not actually occurring from this surface it's occurring from the coating on the back surface and they're fabricated using a technique called float glass where effectively the molten glass is extruded onto a layer of liquid salt hot salt and as it cools the salt layer provides a very very inexpensive way of maintaining a very flat surface so the flattest surface on this piece of float glass is not the front it's the back and so if we use the back surface as a reference plane it's not really necessary for this operation it makes it a lot more efficient and so in order to do this operation what we're gonna do is we're gonna start out with a clean piece of sandpaper I like to start out with about 150 grit for this level of surface quality place it down here and then I'm gonna take an extruded piece of aluminum straight from the mill this piece is not flat the center portion of this piece of aluminum is a little thinner than the outsides it looks sort of like a peanut shape or an hourglass shape if I take this surface here that I'm gonna work on and I draw some pencil lines across here like this as sort of a reference then what I do is I stand by my barrel and I'm going to do this in sort of an elliptical pattern and I will begin by grinding the surface like this on the piece of sandpaper and I'll do this ten twenty thirty times it's not really that critical but after I do this for whatever period of time have decided is a good number then what I'm going to do is I'm going to rotate this in one direction ninety degrees and then I'm gonna walk around something other than 90 degrees and begin the operation again I'm eliminating sort of my biases am i pushing harder with my thumb or my fingers as the paper loading up in certain areas so that we tend to get a very even grind of this piece of aluminum then after a number of grinds or turns like this then what I'm going to do is I'm going to rotate it another 90 and walk around again some other distance other than 90 and begin again but if you take a look after I've done this a little bit you can see the surface has already begun to become much flatter I've asked actually removed most of the pencil lines but you can still see some of the mill lines that are still across the middle that is the deepest part and hasn't yet been ground but I'm pretty close because obviously I've been able to remove most of the pencil I'm going to continue the process now what I'm going to do before I take the sandpaper away is using this arrow as a reference I'm gonna make about six or seven straight strokes in this direction like this producing a linear pattern of grooves that show me sort of what I need to remove in order to get rid of this level of surface damage now from this point on I'm not going to be making the surface in a flatter what I'm going to be doing is I'm going to be removing the pits and the grooves that formed from this sandpaper so I double the grit and I'll go from 150 to 320 I'm going to put this down and this process unlike three or four minutes there will take me all of about 30 seconds this is very fast and because I don't put much Santa much aluminum into this paper I can probably do about 10 or 20 pieces on each grid of sandpaper and if you're doing multiple heat sinks you want to do each grit at a time so that you don't end up contaminating or cross contaminating now I'm probably done you look you'll see all of the linear grooves are gone now with that arrow is my reference I'm gonna do my linear scratches 1 2 3 4 5 6 7 8 9 10 11 12 and you can see that I've now produced a bunch of linear scratches at right angles to my original linear scratches and when I go to the my next grade of sandpaper I'm gonna remove those that was that's I'm almost done with this another minute or two of grinding and this piece will be done now the next step would be to go to 600 and then beyond there a thousand to 2,000 once you go above 600 you probably want to let add a little bit of water to the surface because it tends to clear out some of the debris and keeps the grinding paper clean for a longer period of time bottom line is that when I get the quality of the surface down to about 1500 grit or beyond I don't need to use any thermal interface material if I clamp these together I'm going to beat anything that I can put between here with just the surface to surface contact as an example what I have here is some witness samples that I made using the different grits this is the quality of the surface made with and fifty grit I then carried it over here to the 320 grit on this piece here I have this fabricated 2 600 grit and I then went ahead and brought this up to 1500 grit you can see how much smoother this appears this is good enough now one of the problems you might face however is that you can do this to the heatsink but if you have say a Tec with a aluminum oxide surface is very hard ceramic you can't grind that with the sandpaper effectively and if you've got an expensive CPU you may not want to be taking this thing over to a piece of sandpaper so in that case you're gonna need to use a thermal interface material if you don't care about electrical conductivity then it would highly recommend using a material called indium this is a sheet of indium film it's about 150 microns thick you can get this on ebay full square for about ten bucks it's not expensive indium is an elemental metal that has a melting point about a 350 degrees centigrade and it's extremely soft if you push hard with your finger here the glove won't obviously let me do this I can actually put a fingerprint into this material at a pressure of about a hundred psi or about 1 mega Pascal this will plastically flow into defects between the surfaces and provide an excellent amount of thermal conductivity I'm applying that amount of pressure right now with this pencil 100 psi or a mega Pascal is not that much however for something as large as a CPU that can represent a quarter of a ton so there is an option to this which is made by a company called indium corporation where they make a perforated version of this indium film that has about a 50% fill factor so you only need to use about half the pressure in order to get the plat of the material to flow and even though you'll only get about half the thermal conductivity it's still so superior to these other materials that it still represents a good option the nice thing about indium is not only is it inexpensive but it works from cryogenic temperatures to 300 degrees centigrade it never evaporates it's extremely clean we use it for the laser diodes my son uses it for high-power transistors it's an excellent material now if you're thinking about using say a liquid metal interface material I would tend to stay away from them many of them contain gallium which like mercury is highly corrosive to most metals except for tantalum platinum tungsten it will degrade and corrode the materials so you might get good performance initially but it will eventually eat into the materials now if you're working just say with ceramics or glasses it's a good choice but otherwise I would tend to stay away from this material now if we don't want something that's electrically conductive then we're gonna want to go with either a thermal pad thermal greases or a thermal epoxy now in general I would tend to stay away from thermal pads part of the reason is even though they're tempting because they will make up for very large surface defects they and their adhesive so they'll act as a clamper - you don't have to screw things down they're thick and they have a poor thermal conductivity and so they're better than air but not much thermal greases everybody knows about them they're widely available easily available in thermal epoxies act both as a bonding agent as well as a thermal conductivity agent now one of the sort of issues that you get into when you're using these materials is that this stuff is easily available and it's inexpensive this stuff the thermal epoxy is very expensive and it's hard to get a hold of and for some of our projects where we're going to be building say solar arrays and we want something that acts as a heat adhesive a thermal epoxy we thought why don't we build it ourselves why don't we make it ourselves I'm very familiar with epoxy it's obviously silver so we just mix in blend in some silver powder take the stuff mix it up to the same sort of viscosity as this material put it onto the surface and we should be able to equal what they do you can't it's a lot harder than you might think and part of it has to do with the synthesis when you take the powders and you try to blend them up you can't really get excellent dispersion and at these large firms that make this material they use industrial high shear mixing devices that can take the particles and well into the the third the epoxy or the grease matrix now there's another option and we're going to be doing a video coming up in the near future on the construction of a high-powered ultrasonic cleaner but in learning about the electronics and building the actuators I also fabricated a high-powered therm ultrasonic emulsifier this unit here has about ten to twenty times the amount of energy density per liter is a typical ultrasonic cleaner and actually works as a reasonably good emulsifier the ultrasonic waves will move the particles away from each other and give you a good blend when we mix up some thermal some epoxy with some silver powder we can just about equal to performance of this material when we use this bath for about five or ten minutes and emulsify the materials and disperse them better but what you think about when you're thinking about this you think okay Silver's got a good thermal conductivity but what if I use something that had a higher thermal conductivity than the silver like say diamond I should be able to blow them away right no I can't even though this has much higher thermal conductivity to get an understanding of what's going on here it has to do with the fact that the thermal conductivity between the greases and the epoxies and the powders of the ad mixtures are enormous and to understand that you have to understand the units of thermal conductivity there is a standard called watt meter per degree K and what it means is that if you took a theoretical cube of a material like say copper that was one meter by one meter by one meter and you had a temperature differential across two faces that was equal to one degree K or one C you will have those number of watts of heat that flow through the material and all materials almost every material has a thermal conductivity based on those units silver is the best metal out there at about 420 copper 400 aluminum 200 steel and indium about 90 add a little bit of chromium to the steel make it stainless steel and it plummets to 30 so there's some interesting physics going on there but in the other direction diamond for example has a thermal conductivity of about 1,500 to 2,000 far higher than the silver and graphene has a thermal conductivity of around 10,000 and single wall carbon nanotubes eul's up around 30,000 in the other direction almost every organic whether it's rubber plastic epoxy grease our way down around 0.2 to 0.4 on the same scale it's about a thousand times less thermally conductive than aluminum so the grease or the epoxy the matrix is acting really as an insulator in any of these compounds and it's the powder or the admixture that's doing all the work so with that in mind after testing a huge number of different types of materials and formulas we came up with a better solution this is dendritic copper it is an electrolytic leave grown version of pure copper that has an interesting morphological appearance under a microscope it looks fractal almost like a snowflake or a fern particles are very small but they've got a large extent in one or two dimensions and similarly this is graphene now many of you may know that graphene is a single atomic layer of carbon with a very large XY dimension it looks like a sheet but it doesn't sit flat if you look at this under a microscope it tends to fold and Bend and crumple and so it can interface with other particles in a matrix and produce a lot more surface contact area even though the particles themselves are not massive they're very small what we discovered is that if we mixed up dendritic copper in the epoxy or the graphene in the epoxy we were able to beat the performance of the arctic's silver we found that by blending these the performance continued to improve and when we added a small amount of micro diamond to densify the mixture it improved slightly beyond that now what's happening is even though the materials here are still in an epoxy matrix and even though the heat may have to flow 10 15 a hundred times farther as it's zigzagging its way through these complex particles from surface to surface because the thermal conductivity of this material is ten to ten thousand times greater than the grease it still provides a better thermal interface than say just cuboidal or browned particles that you may have with a silver powder powder or the diamond so what we're gonna do in the description below the video is I will give the recipe that we used for the combination of these three materials as well as the suppliers where we obtain these and you'll be able to reproduce what we do here at home the one thing though you will need access to either a cell disrupter or an emulsifier or a powerful ultrasound to get the kind of dispersion that will produce that increased proto performance over the raw material so with that in mind let's get cooking all right so what we're gonna be using for this epoxy mix is a low viscosity infusion resin the thinner the viscosity of the resin and the epoxy the more of the admixture we can add and the higher the thermal conductivity so I'm going to start by mixing up a quantity of this and this is a three to one so we're gonna go to 50 and 15 so let's see if we can how accurately we can get there and then we're going to add 15 of this to a total of 65 now we're gonna go ahead and blend this up now if we were making this in large quantities what I would do is I would sort of break the typical rule for making epoxy composites and that is I would actually mix in some of my powders into the hardener and some of the powders into the resin itself before I blend this up because it allows me to do a better dispersion in the ultrasound if I don't have a curing epoxy at the same time but in this sort of example that I'm going to show you in the tests it'll still work very well even with a relatively shorter ultrasonic emulsification and this also lets me do a smaller quantity because I don't need much in order to be able to do the test rig good now we're going to add a total of eight grams of the epoxy to here hopefully I get relatively relatively close it isn't bad the finder the scale the more errors you can detect now to that I'm going to add six grams of the dendritic copper this stuff is dense so it doesn't take a lot of volume to do that that's close enough now graphene can be a little bit dangerous and that's because the fine particles can get into your lungs and are not so good a little bit like asbestos it's really only dangerous in the atomized form so once you put it into an epoxy or into a grease it's not going to be a problem but until you do generally speaking not just masks you don't want to get it in your eyes either now to this we're going to end up adding 2 grams of the graphene so the material we have here comes from Israel and it is actually a reduced form of graphene which is much more soluble that's pretty good too and then finally I'm gonna add one gram of diamond so I'm going to bring that to a total of 17 now we're gonna blend this up and once I get the powders to begin to incorporate then the graphene no longer becomes risky and I can take off this annoying mask and goggles yeah please it's safe but it's annoying so we're gonna blend this up and the viscosity with this mixture is pretty similar to the stuff that you'll get in the tubes from Arctic silver and then what we're going to do is I'm going to go around to the ultrasound and get this to disperse better now this ultrasound is so powerful that when I hold the beaker in my hand it actually burns my fingers it's gonna be a little loud I'm gonna use the glove to help Pat it submerge this about halfway down and it really gets thinner too when you put this in here I'm only gonna do this for about two minutes because it actually warms up in here because this is pretty powerful and when I say burning it's not thermal burning it's just the vibration at the point of contacted is gets hot in your fingers I've actually gotten blisters and that's how you can do plastic welding with ultrasound the vibrations actually create frictional heating all right that's about all I can take nice little device and I'll cover how to do that in the next video now we're gonna go ahead and take this epoxy and we're going to prepare the test rig now the way I'm going to do that is I've taken some resistors I got about 50 of these all from the same lot they're 25 watt they're 4 ohm and they're all supposedly within 10% however I found them to be about 1% accurate and it's kind of irrelevant to our test because we're going to run exactly 12 Watts through each one into a water-cooled heatsink and measure the temperature of this after it stabilizes to determine how effectively we're removing the heat so what I'm going to do is take this little stick and I'm going to put on a thin layer of the epoxy to this surface here and it's pretty easy to work with it's a it's a nice it's a nice viscosity it flows very well it's very smooth and one of the tricks to applying any kind of a thermal interface material is thinner is better as long as you've covered the surface you really don't want to glob it up because you're just providing more insulation okay now what I'm going to do is I'm going to turn this over and then I'm going to place this as accurately as I can right in the middle again I don't even know that it's necessary to be accurate but I'm trying to keep everything that I'm doing as consistent as possible in case there is any meaning to the accuracy and then once I feel sort of contacting at a few points is it on a place on this wait which is what I use for each one of these to provide a controlled pressure here we're just gonna let this sit for about three hours four hours until this has cured and then once it's cured we're gonna go ahead and set up the test rig and compare both the plain epoxy to the thermal epoxy from Arctic silver and then a couple of our examples here and just show how well it performs okay it's been about six hours and we've let the epoxy harden up and then what we're gonna do here is to test this I've got the resistor hooked up to a controlled power supply and I've adjusted this to produce as close as I can to exactly twelve point zero watts the slight variations between the resistors in their manufacturer is compensated here because when I do the calculation I'll come out to within a percent or two of that same amount of power dissipation in the resistor the resistor is obviously glued down to this water cooling block and the water cooling block then has a high volume of flow that's delivered from this jus labo lab chiller that maintains the temperature here at exactly 16 point zero degrees for a baseline and because of the high volume even though we're dumping 12 watts in here the base is going to be extremely close to that 16 point zero degrees now what I have here is an IR temperature probe with little spacer stick to maintain a consistent distance across the different test samples well it's been about 10 minutes actually of stabilization I even try to standardize that and we'll see what kind of temperature we get here there's a slight variation depending on position but it's not big and we're getting about seventy four point four degrees seventy four point six now what I'm gonna do is I'm going to remove this here seventy five even we'll set this all up give it about ten more minutes to stabilize and we'll test the Arctic silver okay it's been about ten more minutes and if you see we're still running at twelve point zero degrees I have twelve point zero watts and within a tenth of a degree of sixteen point zero so now this is the Arctic silver and we're going to do that same sort of temperature measurement with a little probe seventy two point three seven two point five it's about the highest I can get so it's definitely better than the epoxy okay it's been about ten more minutes this is the third test this is the system that we built up mixed up before earlier in the video and as you can see we're still at about 12 watts if anything we're actually slightly above at about twelve point two watts and this temperature is still at sixteen point zero degrees and we'll go ahead and temp test the temperature here with our little probe sixty seven point two so despite running a little bit more power through here we still have substantially lower temperatures so that's pretty much it this does work and even if there's a slight imperfection in terms of the precision of this device the power supply obviously we're a little bit conservative and actually ran the power up a little higher here and this machine here which is quite accurate the differences between the three different examples that we produced here are substantial enough that I believe I can say with pretty high confidence that what we made is substantially better than the Arctic silver as a matter of fact the difference between the Arctic silver and this is actually larger than the Arctic silver and just plain epoxy in the description below I've given the recipe and I will provide to provide the suppliers so you can obtain this and you can actually do this at home one of the things you might find a little bit problematic is the dendritic copper comes in a variety of different forms some look a little bit like pockmarked bb's and is not very dendritic and some the very lightweight version which is the very filigree type of material as the material that we used nevertheless will provide you the link so that you can obtain the right copper and the graphene and the diamond if you want to and you have access to an ultrasound to do the emulsification you can make this up yourself but if it turns out that you don't want to obtain quantities of this material and you don't want to invest in an ultrasound will actually sell this material we can mix up the material similar to the way that to the arctic silver people do in syringes and we'll provide you more of it for lower cost through our website you can take a look at this you can compare this to their material see if if it helps you with your projects and it helps to support the channel so hopefully you'll find the video at least interesting potentially useful I want to thank you very much for watching this is a lot of fun I enjoy doing this and if you did like it please give us a thumbs up and more importantly if you interact with a channel if you give us a comment even something as simple as hey it was kind of interesting and you know thanks for the the information that helps the algorithms with YouTube to promote the channels with that level of interaction we hopefully will we'll get some more views and a little bit broader exposure to what we're doing if you like what we're doing on the channel subscribe hit the bell get all notifications to make sure you get notified about new videos and all of that helps us to expand to grow and to afford to buy some of the expensive equipment that we use in our videos so I want to wish you a very good evening we'll see you soon and good night [Music] you

Channel: Tech Ingredients

Views: 309,030

Keywords: Epoxy, Thermal paste, Thermal grease, Thermal epoxy, Arctic Silver, Thermal pad, Indium foil, Dendritic copper, Graphene, Diamond, Ultrasonic mixing

Id: 8MOTMq9g8Nk

Length: 31min 27sec (1887 seconds)

Published: Thu Feb 27 2020

Reddit Comments

[u/MesaEngineering]

What were the results?

[u/TargaryenTurtle]

Thought it was heroin for a sec

[u/fistymcbuttpuncher]

Dude looks like he could be Stephen Colbert's older brother.