Thanks Dewey, We're currently trying to get confirmation of the laminate
material used, it was not supposed to be FR4, but something approved for
4 Lead Free assembly heat cycles (2 reflow, 1 wave, 1 rework). Also one
board is being sent to a third party for a failure analysis.
- Jon
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Whittaker, Dewey
(EHCOE)
Sent: Tuesday, October 31, 2006 10:22 AM
To: [log in to unmask]
Subject: Re: [LF] Lead free parts falling off boards
You have had many good answers to your question on the part/pad
separation issues. The failures of the pad coming off the laminate were
not addressed.
Was the pad/laminate separation an adhesive or cohesive failure?
Was the laminate a high Tg(170 C or higher) FR4?
Was it a Dicy or non-Dicy cured laminate?
There have been failures seen with the use of the Uber Polymers for
Lead-free use, where the materials are so robust they do not yield. With
no relief the laminate fractures and the pad comes off with part of the
laminate. This is a cohesive failure known as cratering.
Work is being done to eliminate this problem.
Dewey
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of DeGenova, Jon R.
Sent: Friday, October 27, 2006 11:19 AM
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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