Hi Al!
We had a similar problem a couple of years ago. Our via oozing problem
showed itself after being built and after thermal cycling.
The vias that were tented with mask were the ones that oozed this black,
dark
stuff, and sometimes blew the tent off the via! I got some pictures that I
just took
(I still have one of the assemblies), that shows this problem. Go to:
http://www.stevezeva.homestead.com and look at; "Via ooze, and Via ooze
2".
Now keep in mind, these vias are tented...the board in the photo is also
conformal
coated with an acrylic...
We did what you did, we scrapped all the assemblies from that lot of bare
fabs that
we got from the vendor, and got them to eat most of the material costs and
labor that
we put into the boards...didn't get them to eat everything though
(bummer!).
We "SCAR'ed" the board vendor, and got an answer back that I wasn't very
convinced
that correctly explained the problem...they said it was oil. I never had
the boards analyzed
because we simply scrapped them and built new ones...so I can't say for
sure if it is really oil.
Kind regards,
-Steve Gregory-
Senior Process Engineer
LaBarge Incorporated
Tulsa, Oklahoma
(918) 459-2285
(918) 459-2350 FAX
|---------+---------------------------->
| | Al Onderick |
| | <[log in to unmask]
| | OM> |
| | Sent by: TechNet |
| | <[log in to unmask]>|
| | |
| | |
| | 05/04/2005 09:06 |
| | AM |
| | Please respond to|
| | TechNet E-Mail |
| | Forum; Please |
| | respond to |
| | al.onderick |
| | |
|---------+---------------------------->
>--------------------------------------------------------------------------------------------------------------|
| |
| To: [log in to unmask] |
| cc: |
| Subject: Re: [TN] Via contamination |
>--------------------------------------------------------------------------------------------------------------|
Originally we thought they were silver. They are Immersion White Tin.
We've decided to scrap the whole lot.
-Al Onderick
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: Wednesday, May 04, 2005 3:34 AM
To: [log in to unmask]
Subject: Re: [TN] Via contamination
Are these boards Immersion Tin? We had a similar problem with some Tin
PCB's
where the Tin chemistry was being left behind in the tented vias and then
erupting during reflow. Check with PCB supplier.
Mark
===== Original Message from [log in to unmask] (TechNet E-Mail Forum) at
3/05/05 16:40
>Greetings Tech netters,
>
>
>
> In the past we've had problems with tented vias not
completely
>tenting and trapping liquid. The liquid would boil and find its way to
>the surface of the board.
>
>
>
>While this looks similar these vias were not tented.
>
>
>
>
>
>http://www.texas-gold.org/PCB/
>
>
>
>Al Onderick
>
>National Instruments
>
>
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