Arlo's power stage.... New pics and video on page 22 + 24

[bearing]

2-5 times less thermal resistance than copper

Good find!

Imagine if there were PCBs made with this stuff as core. Then you could make high power electronics with surface mount transistors instead of the big through hole ones. That way you could put more transistor in a small space, to get better current sharing. With a big heatsink on the bottom side of the PCB, cooling of the SMD components would be as good as, or better than, a TO220 on a heatsink.

[Arlo1]

This might take a while lol but it will be worth it and should not be to bad for replacing fets.

[Alan B]

Good conductor. Hard to solder without overheating the FETs.

[Arlo1]

Good conductor. Hard to solder without overheating the FETs.

I have a plan for that

[Arlo1]

2-5 times less thermal resistance than copper

Good find!

Imagine if there were PCBs made with this stuff as core. Then you could make high power electronics with surface mount transistors instead of the big through hole ones. That way you could put more transistor in a small space, to get better current sharing. With a big heatsink on the bottom side of the PCB, cooling of the SMD components would be as good as, or better than, a TO220 on a heatsink.

It doesnt conduct electricity as cood as copper...

[Arlo1]

Tomorow I will drill and tap the heat sync and solder it all together and build the driver stage!!!

[parabellum]

It doesnt conduct electricity as cood as copper...

I imagine that non conductive type just has a tin layer of other non graphite stuff inside or outside. I wonder how heat conductive it is and how many volts it can handle before spark jumps, also how resistant to cuts of sharp transistor edges.

[Arlo1]

It doesnt conduct electricity as cood as copper...

I imagine that non conductive type just has a tin layer of other non graphite stuff inside or outside. I wonder how heat conductive it is and how many volts it can handle before spark jumps, also how resistant to cuts of sharp transistor edges.

The backs of these IRFP4668 fets are metal in the center with plastic on the edges. Its all listed on the data sheet for heat transfer rates. And the way I made my layout is for the back of the fets TO conduct as well as the drain leg, I will test it with just metal on metal and Krypton paper in between the plates for now.

[Arlo1]

I just found this stuff its price is cheeper and the specs are better. http://www.digikey.ca/ca/en/ph/LairdTec ... eries.html
I also ordered some t gard for the plates.

[Teh Stork]

I really like your layout. Nearly the same as I've got here in my notes, will post it up later

As far as soldering problems go: I would try to get some 43Sn43Pb14Bi, it melts at 163 degrees C, and have good mechanical properties. (similar to 63Sn37Pb, but 20 degC lower melt temperature). Bismut allyos aren't THAT expencive, but Indium totally is xD

[bearing]

2-5 times less thermal resistance than copper

Good find!

Imagine if there were PCBs made with this stuff as core. Then you could make high power electronics with surface mount transistors instead of the big through hole ones. That way you could put more transistor in a small space, to get better current sharing. With a big heatsink on the bottom side of the PCB, cooling of the SMD components would be as good as, or better than, a TO220 on a heatsink.

It doesnt conduct electricity as cood as copper...

The idea was to replace the core of the board (normally FR4 glass fiber or similar) with this stuff (the insulated variant). If you use thick copper it will handle large currents (maybe have to mill the board instead of etching). You could then surface mount and reflow solder the board, just as in a standard SMD process.

[nieles]

I just found this stuff its price is cheeper and the specs are better. http://www.digikey.ca/ca/en/ph/LairdTec ... eries.html
I also ordered some t gaurd for the plates.

you need a electrical insulator right?

this material is electrical conductive

[Arlo1]

I just found this stuff its price is cheeper and the specs are better. http://www.digikey.ca/ca/en/ph/LairdTec ... eries.html
I also ordered some t gard for the plates.

you need a electrical insulator right?

this material is electrical conductive

Under the fets I need both thermaly and electriclay conductive. SO Thats why I ordered the TGON 805 then I need thermaly conductive but electricaly insulative between the plates So thats why I ordered the Tgard T52

[Arlo1]

I just looked at the specs again for the TGON 805 and it may not be better then the Panisonic PGS but its the same material. I was tricked a bit by the spec being listed for a clamping force of 100psi. Its all good though it looks that graphite is the best we can get besides diamond. It also lists both Z and X/Y thermal transfer ratings as well.

[Arlo1]

Sweet the shaft for my big dyno is done I am off to my nabours shop to pick it up and use his brake and slicer to finish this and then tonight when the girlfriend gets home I will re assemble it with Kapton for now.

[nieles]

i was looking around for specs on the tgon 805 material, and found this interesting nasa test on thermal pads:

http://ntrs.nasa.gov/archive/nasa/casi. ... 072659.pdf

[Arlo1]

i was looking around for specs on the tgon 805 material, and found this interesting nasa test on thermal pads:

http://ntrs.nasa.gov/archive/nasa/casi. ... 072659.pdf

Very cool The TYGON 805 is better then bare lol. I was worried at first. I cant wait for it to come in.

[Arlo1]

Just spent about 20 hours building this in the last couple days lol But the nice thing is it shoud last for ever and replacing fets should not be to terable!
Oh and the roller is done for my dyno all I got to do is build the frame for it to spin in.

[Arlo1]

so a quick google search shows me the square cap I used is a .001uf 200v cap p#CK05BX102M
And the round one says K2K on one side and 471 on the other side which google tells me is 470pf but I cant find the voltage.... I used two of each for this power stage. I just want to make sure all caps are good to 200v or more.
According to this table its 400v??? Type K and orange so 400?

[zombiess]

Are those non polar caps large enough? They seem on the small side to me. What material are they made of? Polypropylene, ceramic or polyester? I went with all 1uF 275VAC Polypropylene caps for my power stage as you've seen in my previous thread because I wanted to make sure they had a low ESR and could react fast enough to the spikes. Each phase of my controller is designed with 4uF of these caps with two 1uF on each end of the rails.

Bigmoose recommended I used tabbed pulse rated low esr caps but I didn't have the space for them so I went with what I think will be adequate, but I'm not as far along as you are yet with that power stage.

[texaspyro]

Those look like 50V or less caps...

[Arlo1]

Hu I will try to find some good ones for the small ones tonight... Maybe in an old power supply I will have a couple... Other wise its an order and wait thing....
I want to get this running and I think im ready other then some wires from board to board and the final assembly with the isolation paper that just came in.

[Arlo1]

Guess what came from digikey today lol. Man that was fast. So its all done other then some longer screws and a couple better caps. Oh and some ribbon wire for these sweet connectors I got it will be nice and Clean I like! The graphite paper is pretty cool you can put it on the heat sync and feel the temp of the heat sync throug it instantly!

[Arlo1]

I just found multi color flat twisted ribbon SWEET got some coming no more mess of wires everywere!
http://search.digikey.com/scripts/DkSea ... &x=11&y=15

[Lebowski]

after installing the graphite sheets, I'd measure everything before powering it up
just to make sure it really does isolate the way you expect....

cool caps, I had some of those 20 years ago when I build a vacuum tube radio transmitter,
it had a 1200V 1Amp supply, used 4 caps in series with ballancing resistors. The caps
were pretty big so it took a long time to discharge and make the supply safe to work
on. I had all the caps with the screw connections on one side of a plastic plate, I used to
drop a metal plat on it to discharge them (went with a bang I might add )