TECHNET Archives

July 2002

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Earl Moon <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 2 Jul 2002 13:34:19 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (99 lines)
This is very good input.

Thanks,

Earl Moon

----- Original Message -----
From: "Dave Chapman" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, July 02, 2002 12:40 PM
Subject: Re: [TN] Shelf life of Immersion Silver Fabs


> Mac Dermids processing guide speaks specifically about packaging
> requirements.
>
> Our company just issued instructions to our boardhouses as to packaging
> for Alternate finish boards. Boards must be packaged in lots of 25
> generally, although 10 to a pack is acceptable if they are larger boards
> and more than 25 if they are smaller than 2"X 2". This is standard
practice
> at our houses and we assume at most others. We dont want to open every bag
> of boards for inspection so after QC checks a few boards at incoming we
> will reseal them. This includes boardhouse over runs left on their shelves
> for planned release shipments.
>
> the board house must put a paper date label on the outside of all
packages.
>
> The top and bottom board in the package must be covered by sulphur free
> paper. (Since Immersion Silver finish is below the board surface we are
not
> worried about surface scratches) Plastic will tarnish boards surface.
>
> I have 30 Silver boards in my desk wrapped in paper. They have been there
> over 1 year. The top and bottom boards are very tarnsihed but all the rest
> are fine.
>
> Packages must be vacumm sealed. ( if house has those capabilities
otherwise
> we will seal them at receipt)
>
> Another caveat is if you have to deal with a boardhouse which sends the
> boards out for processing. Legend print is recommended before Immersion
> Silver is applied since chemicals or heat used in screening can cause
> tarnish, staining and unsolders unless they are using a UV ink.
>
> No dessicant is to be inserted inside vacuum sealed packs but is allowable
> inside packing boxes.
>
> The secret to success is to treat all boards as if they are Silver
> Immersion, this avoids tricky document changes and special handilng
> procedures on the assembly floor. Operators should not be touching any
> boards surface with bare hands, washing should be kept to a minimum on All
> boards.
>
> We are having a very positive experience with Immersion Silver transition
> from HASL. 15 assemblies which were problems before are now switched over.
> All BGA boards and anything with 20 mil fine pitch is automatically Silver
> Immersion. We use both Alpha Level and Mac Dermid processed boards.
>
> Aperture selections of stencils for fine pitch is where we are
> concentrating now, since you are starting with 50% less solder you need to
> increase the stencil aperture size but on fine pitch with a 1:1 ratio you
> have shorts on everything less than 20 mil spacing. Better to get shorts
> than opens but we want to reach the perfect balance. If anybody is already
> there would appreciate the feedback, if not we will post it when we get
> there.
> Dave Chapman
> Circuit Service
>
> --------------------------------------------------------------------------
-------
> Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt delivery of Technet send e-mail to [log in to unmask]:
SET Technet NOMAIL
> To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
> Search the archives of previous posts at: http://listserv.ipc.org/archives
> Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
> information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
> --------------------------------------------------------------------------
-------
>

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------

ATOM RSS1 RSS2