I don't really understand your thinking here, I assume you are going to
solder the heat sinks to the heat source. If this is the case then lapping
the solder would be somewhat of a waste of effort as the next thing you will
be doing is melting it.
In answer to your question about chemicals however: Usually you need to use
a flux when soldering.
So far as the aluminium is concerned the flux you would need to use has to
be specially formulated for aluminium and therefore extremely aggressive, [I
don't think I would want it on an electronic assembly]. Having got you
solder on to the part You would need to wash it off in water and then use an
electronic grade flux to fix the tinned heat sink to the part.
I suppose you are looking for metal to metal contact as this would give a
small thermal gradient through bond line. If there is mechanical fixturing
what some people do is use an indium shim. The indium is soft enough that it
will conform to any surface irregularities and lack of flatness. Thermal
conductivity of indium is relatively high and being soft it will take up TCE
mismatches easily. However you would only do this is you really needed the
performance gain, indium is relatively expensive.
Regards
Mike Fenner
Applications Engineer, European Operations
Indium Corporation
T: + 44 1908 580 400
M: + 44 7810 526 317
F: + 44 1908 580 411
E: [log in to unmask]
W: www.indium.com
Leadfree: www.Pb-Free.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Phil Nutting
Sent: Monday, February 24, 2003 4:01 PM
To: [log in to unmask]
Subject: Re: [TN] off topic, more plating (kinda)...
John,
Wow, That seems an excessive amount of work for a heat sink finish. What is
driving you to go to this level of finish?
We have upped or tightened our heat sink surface specs at quite a
significant cost and I can't say that it has made a significant improvements
in performance for the cost. I believe that the biggest offender for us has
been contaminates (dirt, metal chips) under the Isostrate thermal transfer
material that has caused a punch through during a Hi-pot test.
Phil Nutting
-----Original Message-----
From: Grabski III, John R. [mailto:[log in to unmask]]
Sent: Monday, February 24, 2003 10:15 AM
To: [log in to unmask]
Subject: [TN] off topic, more plating (kinda)...
We have a roll of silver solder in house, and I want to try a little project
with a couple heatsinks...
One's copper, the other is aluminum... They've been lapped, and have
near-mirror finish... I'd like to take 1/32" off both and drop on an even
coat of this silver solder... I don't know how well they will bond, and
wonder if some chemicals will need to be used to aid in the bonding
process...
Or do I just let it drip onto the surface??
After the silver's on there, I'm gonna lap THAT finish to mirror-ish quality
and run some temperature tests...
Any advice??
Best Regards,
John Grabski III
Badger Technologies, Inc.
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