We have experienced problems with ENIG and LF which resulted in parts
falling off - the chemistry was from a major player and no definite
conclusion ever reached on the reason. Some ENIG can be porous and
result in oxidization of the under laying Nickel - parts may appear to
be soldered ok but give them a tap and they fall off!
We had been using ENIG on a routine basis for well over 14 years on SnPb
assemblies so were very conversant with the issues ENIG can present.
With LF on the horizon we trialled immersion silver, were very pleased
with the results and in nearly all cases have transitioned designs to
silver.
I would suggest you try silver as well as working with your board vendor
to determine the root cause with your ENIG.
Regards,
Chris
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of DeGenova, Jon R.
Sent: 27 October 2006 19:19
To: [log in to unmask]
Subject: [LF] Lead free parts falling off boards
We have some PCB assemblies, measuring approximately 11x13 inches in
size, .062" thick, with very dense population on both sides. They are
mostly SMT, including about 3 BGAs. These ran fine on as leaded boards,
but in our first runs using a lead-free process and an ENIG board finish
we're seeing a strange problem. Reports are that parts are 'falling
off', not in large numbers, but enough to raise an eyebrow. Mostly
these are passives that are coming off after a double reflow process
(there was no wave soldering done on the boards at the point that this
was noticed). And in some cases, the entire PAD was coming up off the
circuit board. Has anyone seen similar issues? I'd like to give our
assembly personnel some advice on where to start investigating.
Thanks,
Jon DeGenova
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