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What the best way to mount HIGH voltage semiconductors to grounded coolers?
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coppercone2:
I am pretty sure though that you want to use a tensioning bar or one of those special heat sink clips to tension the package rather then a screw for optimal heat conduction
Wolfram:

--- Quote from: floobydust on November 17, 2018, 11:14:14 pm ---I would look at what the automotive industry is using.
Anyone know what Tesla Motors used here in older Model S?  I think it's a modified TO-247 IGBT package.  I couldn't find pics of the other side.

--- End quote ---

That's a Roadster inverter phase leg. This inverter used some polymer based insulation between the IGBTs and the water cooling blocks, and these are failing in large numbers: https://teslamotorsclub.com/tmc/threads/roadster-pem-failure.88028/ . The Model S uses 0.5 mm alumina pads and I haven't heard of them failing. I'm not aware of any pictures of them as the whole phase leg assembly is potted in silicone gel and removing the transistors is a pretty destructive affair.
Zero999:

--- Quote from: NiHaoMike on November 17, 2018, 07:38:25 pm ---Something else that can be done, if the thermal conductivity of a thermal pad is not good enough, is to mount the transistors or whatever on a block of aluminum or copper, then use a larger thermal pad to couple that to the heatsink.

--- End quote ---
Yes, that works very well. In the past I soldered an LM317 to a piece of copper bar which I then fixed to the case with an electrical insulator sandwiched in between.

I was still learning when I built this, so don't give me too much grief about the messy construction.


I repeated the project but made it dual rail, tracking and fixed the LM317 and LM327 with screws to copper blocks, again mounted to the case with electrical insulators. It's a little neater, than the previous project, but could've been better.


Obviously for 600V, the above examples are inadequate. The insulators need to be larger than the copper blocks to ensure adequate creepage distances.
coppercone2:
I don't think solder is permitted for earth ground connections officially, because of mating cycles and flex of the ground pin if the cord is fucked up. The solder lug on the chassis is a bit more acceptable because that point is not being flexed, but you obviously still need excellent strain relief so the motion does not transfer through the ground wire from the plug (which is less if you use multi strand wire).

and the earth solder joint in the lower picture looks down right suspicious. I think you should at least make a half hook through the hole to solder it with good clearance to the pin if you insist on soldering it, it looks like its bearly  attached. Did you clean and flux the joint (perhaps with a brass brush?). The wetting on your solder joints looks horrid but I am not sure if its a camera thing.


Also, where are the fuses at?

cant hurt to put the levitating rectifier on a bracket either.

Also would recommend a softer dielectirc between the torroid and the tensioning washer.

also are those earth ground lugs star washered?

This one is unnecessary but there is a kind of cheap trick to wire-pcb junctions, where you drill a hole away from any conductors and zip-tie the wire to the PCB through the holes or between the hole and the edge of the PCB. It works very well I had a hobby project that got yanked very hard and it held up fine without damage to the PCB.
Gyro:

--- Quote from: Hero999 on November 18, 2018, 08:18:10 pm ---
--- Quote from: NiHaoMike on November 17, 2018, 07:38:25 pm ---Something else that can be done, if the thermal conductivity of a thermal pad is not good enough, is to mount the transistors or whatever on a block of aluminum or copper, then use a larger thermal pad to couple that to the heatsink.

--- End quote ---
Yes, that works very well. In the past I soldered an LM317 to a piece of copper bar which I then fixed to the case with an electrical insulator sandwiched in between.

I was still learning when I built this, so don't give me too much grief about the messy construction.


I repeated the project but made it dual rail, tracking and fixed the LM317 and LM327 with screws to copper blocks, again mounted to the case with electrical insulators. It's a little neater, than the previous project, but could've been better.


Obviously for 600V, the above examples are inadequate. The insulators need to be larger than the copper blocks to ensure adequate creepage distances.

--- End quote ---

"I was still learning when I built this, so don't give me too much grief about the messy construction."


Wouldn't dream of it, but I think you owe it to the forum to post the picture in the 'ugly-but-flawless-project' thread for posterity - if only for the 'securely bolt the lightest components and glue the heavy ones' methodology. Sorry, I really couldn't resist  ;)

https://www.eevblog.com/forum/chat/show-us-your-ugly-but-flawless-project/
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