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Heat spreader plating for good adhesion

Hi,

I'm looking for help on plating of a metal block to be used as a heat spreader. The block is .5" x 1" and .4" wide. A die, dissipating 10 watts, is to be mounted on the .4" wide side using a silver-loaded adhesive, which has a thermal conductivity of 25 W/m-K. However, experiments have shown that unless adhesion to the heatsink and die is very good, poor thermal performance will result. In addition, the volumes for this block is into the millions, so the plating scheme has to be very inexpensive (<$.35/block). My questions are:

1) What type of relatively cost-effective (forget gold) electrically conductive plating will provide the best surface for adhesion? This plating must be thermally very good, similar to aluminum or at least not very thick. Any pricing comparisons would be nice.

2) Would selective plating help reduce cost? The area of plate would be .1" x .1".

Thanks very much in advance for any help.

don h [last name deleted for privacy by Editor]
San Diego, California
1998

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Don,

Based on the information provided, I would guess that electroless nickel would be the optimum. Silver is another possibility.

There are a few companies that could barrel plate the part at a very competitive cost. If the part is aluminum, there are a lot less that could do an excellent job. There are a goodly number that could rack plate them at a slightly higher cost per part, but still under $0.35/part.

Selective plating is a possibility, but shape is everything for that, and probably would end up costing as much.

Finally, why do you want to plate it if it is to be glued on?

James Watts
- Navarre, Florida
1998

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Don

What material is the block made from?

Michael Shane
- San Diego California
1999

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Hi Don. This sounds like a component that would be aluminum. If my guess is correct, you might search "adhesive bonding". Gluing to anodized aluminum or, best, phosphoric acid anodized aluminum, should give the strongest possible bond. And if the anodizing is phosphoric acid anodized, or any thin anodizing, the thermal performance shouldn't be much different than bare aluminum.

If you do decide on electroless nickel plating, I think I'd slightly disagree with the very knowledgable Mr. Watts about the cost of selective plating. When you are doing "millions", you can afford fixturing and automation that will make plating a .1" x .1" area quite a bit less expensive than plating the whole block. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 13, 2012