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June 2006

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Subject:
From:
Genny Gibbard <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Genny Gibbard <[log in to unmask]>
Date:
Thu, 1 Jun 2006 09:19:54 -0600
Content-Type:
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This is very timely.  We have just been realizing that we have no formal
handling procedures in place for the newer finishes, either.  We have
used the robust HASL finish for so long, I don't think people realize
how different these PCB's can be.
Can you tell me if you have any guidelines for Immersion white Sn
finish, as well?  Or is the information below applicable to that as
well?  We had a board supplier tell us that ImmSn needs silver saver
paper as well.
The idea of getting them packaged in small quant's from the manufacturer
is a great idea, as well.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Franklin D Asbell
Sent: June 1, 2006 9:00 AM
To: [log in to unmask]
Subject: Re: [TN] Packaging requirements for IAg Finished PWBs

Yes, we use a neutral pH paper, almost like tissue paper and fold 10 bds
max into bundles, then package these in neutral pH plastic bags.

Scratches are not so much this issue, it's more of abrasion prevention
as well as protection from the environment. We have customer's however
that once the product is received they completely remove the product
from the packaging and place them open in bins until use.

As a practice we pass along assembly and handling guidelines to all
customers who request silver finish for the first time, and with new
customers order silver finish product.

Silver finish reacts to atmosphere more dramatic than tin-lead, the
tin-lead finish is also more durable and less affected by handling,
contaminates, etc so more controlled measures must be taken with silver
finish.

Also, it is best to perform the silver finish process as close to the
end of the fabrication process as possible. We typically perform this
process after rout and final inspection. Silver finish is applied, tape
testing and visual inspection is performed and the product is
immediately packaged.

The following is an excerpt from such a procedure.

==============
5.0     Handling, packaging, and storage

5.1     It is recommended that gloves be used for all handling after the
immersion silver process.
5.2     Salts and acids from fingerprints may tarnish the silver finish.
5.3     Surfactants and/or acid cleaners should not be used on silver
finish
boards. Clean only with DI water rinses.
5.4     Silver plated boards should be packaged as soon as possible to
avoid
exposure to sulfides and chlorides in the air.
5.5     Bundle wrap silver parts in clean acid/sulfur free paper.
Neutral pH
paper is sufficient.
5.6     Storage should be in sealed neutral pH plastic bags to eliminate
direct contact with the air.
5.7     Do not allow sulfur bearing plastic to contact the silver
finish.
5.8     Do not use desiccant in the packages with silver plated boards.
5.9     Do not use rubber bands on boards. Most rubber bands contain
Sulfur
compounds.
==============

Franklin


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Gary Camac
Sent: Thursday, June 01, 2006 9:47 AM
To: [log in to unmask]
Subject: [TN] Packaging requirements for IAg Finished PWBs

Good morning all,

I am struggling through a rewrite of our material specification for
PWBs.  I have seen the recommendation that cover sheets and interleaf
sheets should be used to prevent scratches on IAg finished PWBs.  Have
those that are using IAg seen this as necessary?  We eliminated this
requirement on Sn/Pb finished PWBs some time ago without any negative
effects.

Thanks,

Gary Camac

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