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Old 4th December 2006, 04:20 AM   #1
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Default LM4780 insulators?

The large TO_220 is an unusually large die.
The generic one-size-fits-all insulators are not ideal.
Q-Pad materials are carbon fiber based, and are electrically conductive.

So what's the alternative? .... silpad in sheets?

What are you using for LM4780 insulators?
Part numbers?
Suppliers?
Bulk materials?

Anyone have some extra stock laying around?
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Old 4th December 2006, 09:17 AM   #2
VLSI is offline VLSI  Australia
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I use Mica washers for the MT-200 package (used for 2SA1216/2SC2922 etc.) itís not perfect, as the whole spacing should be 1mm wider.
I have mounted about 8 LM4780 devices so far and have had no trouble with them (yet)
Use the best thermal conducting paste you can find, Try the silver loaded stuff for a computer CPU.
Also you could try mounting the LM4780 directly to a good size chunk of thick copper (with paste) and then insulate that from the heatsink.
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Old 4th December 2006, 10:08 AM   #3
Nordic is offline Nordic  South Africa
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Its a shame the sinks are made of aluminium otherwise you'd love Coollaboratory Liquid Pro

Click the image to open in full size.

Sadly this stuff will eat regular heatsinks for breakfast.

Quote:
"Coollaboratory liquid metal" consists of a liquid metal alloy at a 100%. It does not contain any non-metallic additives like silicone, oxides etc. It does not include any solid components either. Due to this composition, which is completely new for heat conducting pastes, it surpasses the best previously existing heat conducting pastes in the heat conductivity value by the factor 9-10, more simple heat conducting pastes by the factor 100. "Coollaboratory liquid metal" is optimised in its composition for the application with high-quality copper coolers, and can also be used with gold and silver plated coolers (such as some waterblocks).
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Old 4th December 2006, 02:16 PM   #4
CarlosT is offline CarlosT  United States
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Wakefield kapton washers 175-6-280P...perfect for LM3875 and other similar .8" x .8" TO220s.

http://www.wakefield.com/pdf/accessories.pdf
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Old 5th December 2006, 12:14 AM   #5
Minion is offline Minion  Canada
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I have tried Pieces of tempered Glass with heatsink compound on either side and Have gotten fair results.....

The hard part was drilling the Screw hole through the Glass without breaking it but once I got that figured out it actually worked pretty well....


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Old 5th December 2006, 02:46 AM   #6
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For LM3886 and 3875 you can use Bergquist pads. Digikey# BER118-ND is a kapton-based pad (K10). Highly recommend.
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Old 5th December 2006, 05:52 AM   #7
traw is offline traw  United States
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shoot, can not find the baggie with the part number. it was from digikey. search the catalog pages i guess.
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Old 5th December 2006, 05:53 AM   #8
traw is offline traw  United States
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i can mail you this sheet of 4 if you like
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Old 5th December 2006, 11:04 AM   #9
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Digikey BER117-ND
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Old 5th December 2006, 11:51 AM   #10
CarlosT is offline CarlosT  United States
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The Wakefield stuff is cheaper...well like by about the cost of a small cup'o'joe
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