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Date: | Mon, 29 Oct 2007 10:26:08 -0700 |
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To bake or not to bake? Agh, that's the question, whether it's nobler in
the mind's eye to bake and suffer the slings and arrows of solderability
uncertainties or oxidental poisonings; or not to bake and go gently to
that thermal excursion and watery grave of moisture ingression.
The old dicy cured FR4s lulled too many people to idyllic complacencies.
The times are changing and the newer engineered laminates demand proper
attention to detail. Proper handling and storage conditions are
mandatory. Baking protocols will need to consider some of the following:
* Laminate type
* Cure system
* Tg of the laminate
* Design robustness
* PB layer count and thickness
* Final surface finish
* Processing window
* Processing profile(including ramp rate, max. temp., and TAL)
* Compensating factors
Laminates that are destined for High-rel, Lead-free applications will
probably require baking. To paraphrase;
If in doubt
Bake it out
If not
Lose the lot
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joel Alexander
Sent: Tuesday, October 23, 2007 9:23 AM
To: [log in to unmask]
Subject: [TN] Delamination of lead free PCBs
Has anyone experienced an increase of delamination when processing in a
lead free environment. Typically 4 to 6 layer pcbs during SMT reflow. We
are using the high temp laminate suggested for our process. When we
contacted the supplier and they indicated that any PCBs that are over
six
months old should be baked prior to processing. This was never required
with leaded PCBs.
Is anyone seeing the same condition and similar feedback from your PCB
suppliers
Joel Alexander
Quality Assurance Manager
TT APSCO, INC.
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