A common affliction: going in the hole financially, due to post-stress
disorders.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dwight Mattix
Sent: Saturday, November 17, 2007 10:37 AM
To: [log in to unmask]
Subject: Re: [TN] Post Thermal Stress Hole Wall Pull Away Criteria,
cross section analysis
At 07:24 AM 11/17/2007, Paul Reid wrote:
>Hi Victor,
>
>We see a lot of "hole wall pull away" (HWPA) in RoHS applications, and
I
>agree with Werner's statement, but would like to add one more
>consideration; out gassing. Recently some "high end" materials have
been
>producing catastrophic HWPA to the degree that internal interconnect
are
>broken.
gee, Paul -- wonder if you have a particular app of ours in mind. L0L!
On related note, we've observed that some of the higher temp "Pb-free"
laminates are more resistant to traditional hole prep (i.e.
permanganate,
plasma). Take the time to look at hole wall roughness after prep (i.e
SEM)
when you're evaluating a new laminate.
We've observed some plasma recipes actually "polish" some FR4 Pb-free
laminates and make the HWPA worse. A hybrid stackup was used on the
product so some plasma was needed to prep the ptfe laminate to accept
plating. Permanganate wasn't getting it done in that case so plasma was
eval'd (alone and in combo w/ permanganate). After that particular
plasma
process, no amount of permanganate processing would roughen the
surface. The plasma would polish away any roughening when preceded by
permanganate. There were other issues w/ drill profile/smear and
quality
of electroless that had to be improved as well on that project.
Bottomline, don't hesitate to use some tools like SEM to get some a
qualitative view of hole prep and electroless dep.
>Normal HWPA is considered relatively benign, from a reliability point
of
>view, even stress relieving, but if it causes post separation, well
that
>is not benign.
>
>Sincerely,
>
>Paul Reid
>
>Program Coordinator
>
>PWB Interconnect Solutions Inc.
>235 Stafford Rd., West, Unit 103
>Nepean, Ontario
>Canada, K2H 9C1
>
>613 596 4244 ext. 229
>[log in to unmask] <mailto:[log in to unmask]>
>
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]]On Behalf Of Victor G. Hernandez
>Sent: Wednesday, November 07, 2007 10:04 AM
>To: [log in to unmask]
>Subject: [TN] Post Thermal Stress Hole Wall Pull Away Criteria, cross
>section analysis
>
>
>Fellow TechNetters:
>
> Where can I find acceptability for PTH quality?
>
>Victor,
>
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