I'm not making any recommendations, just stating our method.
Many desiccant packs contain sulfur either in the media or paper, you want
to keep sulfur of any type away from any solderable finish, especially
silver.
Vacuum sealing is good if product is going to remain on a shelf for a length
of time. In today's busy facilities product is typically purchased when
needed and used immediately.
If the product being packaged is contaminate free, handled and packaged
properly, and, not subjected to any harsh environment prior to use then in
my opinion vacuum packaging is not necessary.
That packaging method is best agreed upon between the buyer and seller.
I have no opinion on the (in)effectiveness of a dessicant pack in a vacuum
sealed package, I have seen and heard information both pro and con. It is
something that should be agreed upon depending upon how long product will
remain in stock, environment, etc etc.
Franklin
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Amol (349)
Sent: Thursday, June 01, 2006 11:42 AM
To: [log in to unmask]
Subject: Re: [TN] Packaging requirements for IAg Finished PWBs
Hi,
Why do you recommend no desiccant?
Also, are there any distinct pros and cons of Vacuum Sealing the boards vs.
putting them in a plastic bag with proper paper between the board and a
desiccant pack?
I was of the opinion that putting a desiccant pack and then vacuum sealing
does not make sense as there is very little air inside the package, and due
to the vacuum, any moisture would never reach the desiccant pack anyways! Is
there a specific reason board manufacturers package their boards this way??
Regards,
Amol Kane
M.S (Industrial Eng.)
Process Engineer
Harvard Custom Manufacturing
941 Route 38 Owego, NY 13827
Phone: (607) 687-7669 x349
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Franklin D Asbell
Sent: Thursday, June 01, 2006 11:00 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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