Phil,
Thanks for the recognition, but since I have been told that the Technet
police will dole out the punishment, I'll breakdown and resist any
potentially bad humor.
I agree with some of your failure modes. I have also seen failures in PWBs,
where the only difference was the glass to resin ratio. The failure path
appeared to be along the larger glass bundle resin interface.
Dewey
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]]On Behalf Of Anslow, Phillip
Sent: Wednesday, September 01, 2004 8:50 AM
To: [log in to unmask]
Subject: Re: [LF] lead-free PCB source
John,
Your statement "is hole to plane distance dependant," is to an extent
incomplete as CAF is not limited to whether a voltage differential is
between a "plane" and a hole only. When is a plane not a plane? (I can hear
Dewey's replies coming thick and fast). CAF can occur between any
combination of conductors at a PD,RH and separation where there is a path
for CAF growth present and so includes trace-trace, trace-plane,
trace-hole, hole-hole, plane-plane etc (if I missed any). It is also more
prone on woven reinforcement laminates than random fibre materials together
with the factors you mention.
I also understood CAF to be a different phenomenon to those of dendrite
growth or tin whiskers - both of which have had recent strings on Technet
and Lead-Free IPC forums.
Regards, Phil
-----Original Message-----
From: John Burke [mailto:[log in to unmask]]
Sent: 01 September 2004 14:07
To: [log in to unmask]
Subject: Re: [LF] lead-free PCB source
*** WARNING ***
This mail has originated outside your organization,
either from an external partner or the Global Internet.
Keep this in mind if you answer this message.
You actually should design to avoid CAF rather than just choosing a
material. CAF formation is hole to plane distance dependent, varies with the
voltage potential on that plane, and is also humidity dependent on the
working environment that it is put into.
John
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]]On Behalf Of Bev Christian
Sent: Wednesday, September 01, 2004 6:06 AM
To: [log in to unmask]
Subject: Re: [LF] lead-free PCB source
Dear SF,
Your question is extremely broad and I am surprised that you have not sought
out experts in your company that know an incredible amount about this
subject.
In terms of finish ENIG, immersion tin, immersion silver, OSP, HASL (Non
lead containing) and others all work WITHIN CERTAIN MANUFACTURING AND
RELIABILITY CONSTRAINTS. We can't help you without knowing more about your
product.
Any decent PCB manufacturer should be able to offer you one or more of these
finishes on PCBs with higher Tg values. But as the British NPL and others
have shown, higher Tg is not enough to stop the potential for conductive
anodic filament growth.
I think you have a lot of homework to do.
sincerely Bev Christian
Research in Motion
-----Original Message-----
From: No Name [mailto:[log in to unmask]]
Sent: September 1, 2004 5:33 AM
To: [log in to unmask]
Subject: [LF] lead-free PCB source
Hello everyone,
Would someone pls recommend PCB suppliers and surface finish for lead-free
PCB fabrication? Thanks for your help.
Regards,
SF
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