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