No glass fiber brush! Get hold of a horse or pig, with brass handle. For what ever the reason, esd issue is less when use our four legs friends.
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----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Sun Feb 08 12:13:14 2009
Subject: Re: [TN] Part solderability
Hi Graham,
steam test does not tell you much about underlying platings. Namely, if you
are using ceramic PGAs, the pins are nickel plated Kovar with some gold
upon. I have seen something like yours a number of time. It has to do with
bad pretreatment before nickel plating, or bad nickel plating, which is not
uncommon these days. Even plastic PGAs can have bad underplate. My advice:
have a look at some cross sections in SEM/EDAX. Start with a glass fiber
brush (kind of eraser) stroke. If the nickel is anomalous, you'll see it in
a ordinary stereo microscope. If you are used to etching, a number of dips
in a not to concentrated HCl/H2SO4/H2O (strip gold at first of course) will
probably reveal a lot even before SEM. I have some pictures on this, if I
can find them, I'll send a pidgeon.
Inge
----- Original Message -----
From: "Graham Collins" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, February 06, 2009 3:12 PM
Subject: [TN] Part solderability
Hi guys.
A while back I rejected a bunch of parts due to non wetting when we went to
solder them.
The manufacturer has come back with a response to our guys, saying that they
did a steam aging test on them and they passed fine. He wants to discuss it
with us.
Obviously this is not good - they pass his test but I can't solder the
things. Which makes me suspect his test... but makes him suspect my
process. I don't know enough about steam aging tests to discuss this well.
Obviously I need to ask what kind of flux he is using, but anything else?
Our process is SnPb, we use RMA flux, and the wave soldering machine runs at
500F for the pot. This is on an assembly that we have happily built for
about 7 years, with the same manufacturer of part, and no process changes
that I can identify as significant. The part is what I would call
marginally solderable, if we hand solder it and put a fair bit of heat to
the lead we can get it to solder, but not well or easily. No previous
soldering issues with the part.
regards,
Graham Collins
Halifax Production Engineering
L-3 communications Electronic Systems
(902) 873-2000 ext. 6215
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