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head_spaz 4th December 2006 05:20 AM

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?
Bulk materials?

Anyone have some extra stock laying around?

VLSI 4th December 2006 10:17 AM

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.

Nordic 4th December 2006 11:08 AM

Its a shame the sinks are made of aluminium otherwise you'd love Coollaboratory Liquid Pro

An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.

Sadly this stuff will eat regular heatsinks for breakfast.


"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).

CarlosT 4th December 2006 03:16 PM

Wakefield kapton washers 175-6-280P...perfect for LM3875 and other similar .8" x .8" TO220s.

Minion 5th December 2006 01:14 AM

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....


BrianDonegan 5th December 2006 03:46 AM

For LM3886 and 3875 you can use Bergquist pads. Digikey# BER118-ND is a kapton-based pad (K10). Highly recommend.

traw 5th December 2006 06:52 AM

2 Attachment(s)
shoot, can not find the baggie with the part number. it was from digikey. search the catalog pages i guess.

traw 5th December 2006 06:53 AM

i can mail you this sheet of 4 if you like

BrianDonegan 5th December 2006 12:04 PM

Digikey BER117-ND

CarlosT 5th December 2006 12:51 PM

The Wakefield stuff is cheaper...well like by about the cost of a small cup'o'joe :D

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