Nat Semi 60watt LM4780 Insulator

Did you buy it without the insulator? I can't recall buying something like that packaged for OEM that didn't come with the proper insulator.

You can get raw mica at McMaster-Carr:

Or, you could just float the heat sink at +V.

Good Luck! Rich

I read the datasheet and they do not mention a heatsink isolatior in the mounting section. If the part is black plastic all the way around, it doesn't need it. As small dab of the white thermal grease stuff everyone hates is all your need. Putting anything else will degrade the thermal performance.

isolate a

It seems that this is a common problem for this device. The best suggestion is to get a sheet of thermally conductive insulator and cut your own. RS Components have Berquist Sil-pad 400 in 12"x12" sheets for $40.90 + gst.

Go to

A higher quality sheet of Sil-Pad K6 (RS 468-2224) will cost $99.40 + gst.

Thanks for the great suggestion.

All I need to know is it thermal properties.... to take this in to consideration for the heat disipation calculations.

Joe

Sil-pads and kapton ("thermafilm") are rotten heat conductors. The best way to cool a semi is to just use silicone grease and isolate the heat sink. Or hard anodize the sink and use grease. Next best is an AlN or BeO insulator. Thin mica is pretty good.

One nice trick is to mount the semi to a heat spreader block, ideally copper, and use an insulator between the block and the main sink. That increases the area over which the insulator acts, reductig theta proportionally.

John