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August 2006

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From:
Kevin Glidden <[log in to unmask]>
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Date:
Fri, 18 Aug 2006 10:44:53 -0400
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A metallurgist I am not....

We have brass eyelets that we solder wires into.  I am unable to obtain
detailed information on the specific alloy, but the vendor told me it was
70% Copper, 30% Zinc.  We are soldering using 63/37 solder and RMA flux.
During soldering, the eyelet appears to change to copper in the non-soldered
areas.  A brief search of some Tech-Net archives has told me that the Zn
will diffuse out and create solderability problems.  But is the end result
that the material appears to be copper as in my case?

As a side note, I tried a water sol flux and observed the same condition.  I
then tried simply heating an eyelet with an iron - no flux or solder - and
there was no change, so it appears to be flux related.  I also cut a piece
up to verify it is solid brass, not plated.  We tried brushing the eyelet
after soldering and it appears that you can restore the brass finish to some
extend.

Anyway, I have confirmed with the supplier these should have been hot solder
dipped, and we have already ordered replacements.  But I am now faced with a
question I cannot answer - what is the reliability concern of this
phenomenon, if any?  These solder joints get conformal coated, and then the
entire PCB is RTV'd into a case, so it is well sealed.  Can I continue to
use the existing stock, or is this a serious reliability issue?

Thanks!




Kevin Glidden

Manufacturing Engineer



Astronics Luminescent Systems Inc.

4 Lucent Drive

Lebanon, NH 03766



P: 603-643-7766 x3152

F: 603-643-5947



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