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| really proper way to apply thermal compound? |
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| wraper:
--- Quote from: james_s on December 13, 2018, 08:45:01 pm --- --- Quote from: wraper on December 13, 2018, 08:12:47 pm --- --- Quote from: james_s on December 13, 2018, 07:44:57 pm ---Too much paste makes a huge mess all over everything, and in the case of power transistors I've replaced failed transistors that had so much paste that they weren't sitting flat on the heatsink. --- End quote --- If transistors were not sitting flat, it's certainly not because of the amount of the thermal paste. But because they were not mounted properly or were not tightened as should. --- Quote ---I repaired something that was malfunctioning due to conductive paste oozing out on the leads. --- End quote --- You need to buy that crap specially. And those are not even among the best in regards of thermal conductivity of modern thermal pastes. --- End quote --- I didn't mount them, I just cleaned up the mess. These were arcade vector monitors with big TO-3 transistors that screw into flimsy stamped frame sockets. --- End quote --- Please explain how thermal paste can be responsible for gaps? Did I say anything about who mounted them? |
| coppercone2:
well it can seperate and change density |
| james_s:
--- Quote from: wraper on December 13, 2018, 09:35:00 pm --- --- Quote from: james_s on December 13, 2018, 08:45:01 pm --- --- Quote from: wraper on December 13, 2018, 08:12:47 pm --- --- Quote from: james_s on December 13, 2018, 07:44:57 pm ---Too much paste makes a huge mess all over everything, and in the case of power transistors I've replaced failed transistors that had so much paste that they weren't sitting flat on the heatsink. --- End quote --- If transistors were not sitting flat, it's certainly not because of the amount of the thermal paste. But because they were not mounted properly or were not tightened as should. --- Quote ---I repaired something that was malfunctioning due to conductive paste oozing out on the leads. --- End quote --- You need to buy that crap specially. And those are not even among the best in regards of thermal conductivity of modern thermal pastes. --- End quote --- I didn't mount them, I just cleaned up the mess. These were arcade vector monitors with big TO-3 transistors that screw into flimsy stamped frame sockets. --- End quote --- Please explain how thermal paste can be responsible for gaps? Did I say anything about who mounted them? --- End quote --- A thick glob does not always squeeze all the way out, it has some thickness. After removing the transistors I have often seen a thick layer of the stuff, as thick as a piece of paper easily. Not a huge gap but not zero either. Biggest problem though was it made a greasy mess. There is no reason to glop on a ton of it, a little goes a long way. |
| coppercone2:
why? If you measure torque and the threads are clean you should put a surface at a particular pressure. If you have too much grease why would it not work? How does the mechanics of the grease behave ? I am not saying you are wrong but I don't understand it. You are applying a feedback force, with a torque wrench. What you are saying is true if you basically pulsed energy into the system without feedback... but you don't do that with a screw driver, the time constant of the stuff seeping out from under the package and stabilizing should be much faster then the screw driver.. I think about the simple model this way: your hand is the voltage source and your eyes on the torque wrench scale or click of the wrench is the sense wire. You can still get the correct voltage drop despite the increased resistance of flow. I am trying to think about this in terms of deformation and nonlinear forces, maybe there is something else at play here. This is exacty why I started the thread to learn if there is something like that. Some kind of pseudo phase change, mechanical separation, state of matter type thing (kinda far out), etc. Like a non newtonian fluid will resist a impact, if you slam it with the screw driver, but if you are slow it should work the same? Just check to make sure torque did not change after a while and bring it to the same torque... it would have to some how change in its parameters... does this stuff maybe have really really low frequency non newtonian behavior (or what ever the proper term is to describe the impulse sensitivity of non Newtonian fluids towards flow). |
| TinyMirrors:
I'm probably late to reply. This is my favorite way to put on thermal compounds. I put two pieces of scotch tape on the thing I want to put compound on. Like drawing two parallel sides of a rectangle with the tape leaving an area between them to put the compound. Then use a razor blade or credit card to scrape the thermal paste between the two pieces of tape. The tape keeps the razor blade at a very low height as you scrap making a really thin layer of thermal compound. Pull the tape up and have a nice bordered area. If you're really good you can mark off a square with the tape but I'm never that patient and use two pieces of tape. | | | | |T| |T| |A| Compound |A| |P| |P| |E| |E| | | | | |
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