On Jun 29, 9:38*pm, Joseph Gwinn wrote:
In article
,
*"Denis G." wrote:
On Jun 29, 10:23*am, Joseph Gwinn wrote:
In article
,
*George Herold wrote:
(reposted from SED)
I want to try soldering some aluminum plate (0.032˛) onto each side
of
a brass cylinder. *When trying to solder aluminum in the past I
failed. *I think I heard that some Al alloys are easier to solder
than
others. *Išve got a choice (From McMaster-C) of 6061, 2024. 7075, and
1100. * Any idea of which is better?
I was also planning on getting some aluminum flux and some Zn/tin
solder from McM-C. *Other suggestions welcome.
If the temperature coefficients of linear expansion of the brass and the
aluminum don't match to within something like 1%, the joint will surely
tear itself apart, no matter how well soldered the joint is.
Joe Gwinn
I looked to see if I could find for myself criteria for brazing of
dissimilar metals. *I found this:
http://preview.tinyurl.com/6ndm7k3
I thought that a filler metal needed to be a material that could alloy
with the materials being joined. *That's certainly the case with zinc,
brass and aluminum. *It seems to be a complicated subject, but I
expect that he's on the right track (if he can control oxidation and
allow space for the filler and alloying).
For what it's worth, I also found this:
http://www.youtube.com/watch?v=lGy7pHx6P3Y
Interesting book and webpage. *I think I'll read the book.
The issue is not that one cannot braze metal X to metal Y. *For the most
part, you can braze anything to anything. *The issue is that if one does
not design to handle dissimilar temperature coefficients, the joint will
soon tear itself apart.
This is a big issue in high reliability engineering, especially in the
engineering of packages for semiconductors. *There is an
accelerated-aging MIL-SPEC test for such things, where one alternately
plunges a part being tested into hot oil then liquid nitrogen. *If
tempcos are not well matched, the part deconstructs itself. *This is a
very severe test, but is a good predictor of future failure rate.
Especially in power electronics.
Joe Gwinn
I've a little bit of experience with HAST, but nothing as severe as
what you describe. Military stuff is always pushing the limits.