TECHNET Archives

February 2004

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:
Franklin D Asbell <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 10 Feb 2004 10:51:57 -0600
Content-Type:
text/plain
Parts/Attachments:
text/plain (124 lines)
We still have a customer that desires UV mask over tin/lead reflow...he
believes this is the magic cure to a problem he had many years ago with
'noise' on a few boards...we've stopped trying to convince him to go
SMOBC...

Yes, I remember your problems with the dry film mask...as for it not being
as shiny, how long was her board exposed to air before the pictures were
taken, as opposed to your boards?

Poor surface prep is the most common (99.6%) cause of mask failure
documented here at this facility...luckily it is a very rare occurence
anymore...(by the way, did someone ask if we were the fabricators of Sue's
boards...no...not us). This would also include things such as fingerprints
after cleaning, contaminates on the panels after cleaning, etc.

I agree with your comments about LPI durability, it coming off as massive as
that pushes me more towards cure, mixing of the mask, or possibly a
combination. I could not see clear enough for staining (moisture, chemical
residue, other contaminates) but I still would not be convinced it's
contaminate or cleanliness only because the widespread areas...that tells me
look to the mask itself...

still pondering the possibility, wonder if Sue would provide more feedback

Franklin




----- Original Message -----
From: "Steve Gregory" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, February 09, 2004 6:31 PM
Subject: Re: [TN] Solder Mask Flaking


> In a message dated 2/9/2004 4:55:42 PM Central Standard Time,
> [log in to unmask] writes:
> Okay, and those times not 'most often' what are the causes in your
> experience, of flaking mask?
>
> Hi Franklin!
>
> Not sure who you're directing your question to, but I'll tell you my
> experience.
>
> I've just experienced three scenarios for mask failure.
>
> 1. The mask was applied over tin (very old design, and SMOBC wasn't called
> out on the drawing), and it wasn't caught until the assembly was
waved...this
> was was quite a while ago.
>
> 2. Incompatibility with a certain dry film mask and cleaning chemistry. To
be
> specific; Dynachem Dynamask (now Shipley's line since they bought it from
> Dynachem) and Kyzen Aquanox XJN don't like each other.
>
> 3. The last incident was bad surface prep that was acknowledged by the fab
> vendor, and what I have pictures of on my page.
>
> Number one of my three occasions was like I said, a long time ago...nobody
> should see that anymore. I'd like to think that everybody nowdays know
that
> solder mask needs to go on over bare copper.
>
> Number two could happen if you happen to use XJN and have a board with the
> Dynachem dry film on the board.
>
> Number three could happen to anybody if your fab vendor doesn't have good
> checks and balances on the production floor to make sure a step isn't
skipped.
>
> The pictures that Sue sent me, looks like an LPI was used. I have never,
ever
> had any trouble with LPI mask coming off a fab unless it was applied over
> something other than bare copper. This tells me that something wasn't
quite right
> when it was applied. I have a hard time trying to think of what could
cause
> the mask to come off the board the way that it did on Sue's boards during
the
> assembly process. I know you haven't seen the pictures yet, but there's
great
> big areas where the mask came off. The difference between what I saw
between
> her case and mine, was that the copper is not as shiny on her boards as
was
> mine, and to me it looks like a LPI was used...which kind of suprises me.
LPI
> usually is pretty bullet-proof, unless something wasn't right during
application.
>
> My 2-cents...
>
> -Steve Gregory-
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 1.8e
> 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 or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
> 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/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
> -----------------------------------------------------
>
>
>

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------

ATOM RSS1 RSS2