Hi Matt,
I agree 100% with Michael. This condition can be acceptable for 1.27mm
pitch BGA's and/or CCGA's. Indeed, at a previous employer, we used to
specify plugging of vias around the BGA, which inherently causes a 2 mil
soldermask bump. The 'extra' solder paste was accounted for in our
process. At my current employer, we NEVER see the easy 1.27mm pitch
BGA's; everything is 0.80mm or less. High yields at volume are
critical, so a soldermask bump isn't tolerated within a certain distance
of the BGA pads. We didn't get to that specification because our
suppliers told us the spec and the dangers of not following it. First,
we ran into the problem, then we notified our suppliers, and explained
why.
I like to give my suppliers a line tour of our process whenever their
quality and/or technical people visit. They don't know my process and I
commonly need to give them detailed technical explanations of why
certain specification are the way they are and how it impacts our
manufacturing.
Technically, unless they violated your explicit documentation, they're
not culpable. Failure to advise wouldn't hold up in court as making
them culpable.
You don't want to be sole sourced with any supplier on any product.
It's in your best interest to bring this supplier along to knowing how
to build boards that are acceptable to you.
Regards,
Ryan
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Barmuta, Michael
Sent: Monday, March 12, 2007 4:52 PM
To: [log in to unmask]
Subject: Re: [TN] (2) [TN] Paste Volume, off contact vs non off contact
Matt: Never assume. To quote the financial investment guys "past
performance is no indication of future results".
Some fabricators are great others are bucket shops. That's why you need
to take the time to qualify the vendor, work out any issues and specify
the end product. If you don't you're going to get what you get. I
understand that sometimes you don't have the luxury, time or business
strategy to do this.
We've been thru these types of problems many times. If fact we had
problems with exactly what you're faced with, among others. We continue
to work with our suppliers on new designs to make sure what we are
asking for is what we really want and to make sure that our suppliers
actually understand what we are asking for. And when we change
fabricators to some extent it all starts over again. It boils down to
communication.
In the perfect world you shouldn't have to do all this but hey you do
what you've got to do.
Good Luck
Michael Barmuta
Staff Engineer
Fluke Corp.
Everett WA
425-446-6076
-----Original Message-----
From: Matt Kehoe-SIPAD Systems [mailto:[log in to unmask]]
Sent: Monday, March 12, 2007 3:19 PM
To: TechNet E-Mail Forum; Barmuta, Michael
Subject: Re: [TN] (2) [TN] Paste Volume, off contact vs non off contact
I agree with you to a certain point.
The affects of this condition are not unique to my process. Anyone who
printed these boards would have run into the same problem. Building up a
non-planar surface on a board will always result in poor print quality
no
matter who runs it.
Lets turn it around.
Should the vendor, after reading the print, send me an email telling me
that
because the customer has specified covered vias that their "unique"
process
builds up mask to a height of .002 creating a non-planar topography, and
that I might want to use a stencil that is compensated for that? Again,
this
build-up is "unique" to this vendors way of applying mask. All of the
other
vendors we get boards from seem to be able to meet the print without
disrupting the planar surface of the boards.
Should I have to send a letter to every vendor that builds a board for
me
that pizza sauce is a non acceptable material for a circuit board. No.
They
should know that, as well as the situations that non-planar surfaces on
circuit boards can cause.......
I am not on a witch hunt here. I am just trying to get an industry
opinion
and all have been excellent. I don't agree with them all, but they have
been
honest and helpful.
Thanks to all,,,,,, Solder ON!!!!!!
mk
Matt Kehoe
SIPAD Systems Inc.
The "Original Solid Solder Deposit"
360-C Winkler Drive
Alpharetta, GA. 30004
770-475-4576
770-475-1597 fax
www.sipad.com
----- Original Message -----
From: "Barmuta, Michael" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, March 12, 2007 4:12 PM
Subject: Re: [TN] (2) [TN] Paste Volume, off contact vs non off contact
Hi Wayne, Matt: In this particular case I would say that the vendor is
not liable.
This was a new vendor. If you had "qualified" this vendor prior to
production to build the boards in a particular way or call out and they
then sent you boards that did not meet the pre-agreed criteria, then you
would have a case. However this is not how I read situation. I didn't
see anything that said they did not build to print.
You basically get boards from a new vendor and they give you problems
with your process. Not all board fabricators know the limitations of
your processes. Some are better than others.
You need to contact the vendor and discuss the problem, work out an
acceptable solution and document it on the drawing.
If it's a good vendor that wants your business there may be a middle
ground for $cost on a remake or future credit.
Regards
Michael Barmuta
Staff Engineer
Fluke Corp.
Everett WA
425-446-6076
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Monday, March 12, 2007 12:50 PM
To: [log in to unmask]
Subject: Re: [TN] Paste Volume, off contact vs non off contact
I would say it was the vendor's liability, because they did something
which restricted the way the boards could be handled without first
getting an OK from their customer. Sure, the vendor could say that they
didn't think you'd use a stencil for the BGA, but they should've
contacted you if they processed the board in such a way as to preclude
you from using a stencil, which is the industry's standard operating
procedure.
Wayne Thayer
>>> [log in to unmask] 3/12/2007 8:50:23 am >>>
Guy/Gals,
Thanks for the solutions to the problem. I know how to fix it in the
future.
The question I am trying to answer does not have anything to do with
how to
fix the problem.
The question is quite simply, if a vendor supplied boards with this
condition, and it resulted in scrap/rework, would you consider that
your
liability or theirs?
mk
\Matt Kehoe
SIPAD Systems Inc
"The Original Solid Solder Deposit"
360-C Winkler Drive
Alpharetta, GA. 30004
770-475-4576
770-475-1597 fax
www.sipad.com
[log in to unmask]
Please note, Matt Kehoe's E-mail has changed from
[log in to unmask] to [log in to unmask]
This new email is heavily filtered for spam. If your email is bounced,
forward the bounce back text to [log in to unmask] and your account
will
be unblocked.
Thank you for your patience in helping SIPAD Systems combat spam.
----- Original Message -----
From: "Bill Kunkle" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, March 09, 2007 2:11 PM
Subject: Re: [TN] Paste Volume, off contact vs non off contact
> Matt,
>
> I agree with Bill C, stencil relief pockets at the via locations will
> allow
> the high points to be accepted into the bottom of the foil.
>
> Bill Kunkle
> MET Assocs
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Matt Kehoe
> Sent: Friday, March 09, 2007 12:01 PM
> To: [log in to unmask]
> Subject: [TN] Paste Volume, off contact vs non off contact
>
>
> We have been processing a family of boards for 3 years. No issues.
New PCB
> Vendor and the boards suddenly will not print very well. Sloppy
printing
> definition. Heavy heavy deposition.
>
> Closer inspection reveals that the soldermask is built up .0012-.0019
over
> the vias, preventing the stencil from gasketing. Vendor claims they
are
> built to print.. Opinions?
>
> Pictures at ;
> http://www.sipad.com/ssiqa/3942vias.pdf
> http://www.sipad.com/ViasBuildup.pdf
>
> The question we are trying to answer is, if your boards came in with
mask
> this thick over the vias would you feel confident in running them
without
> modifing the stencil? Would you expect a significant increase in
solder
> volume?
>
>
> mk
>
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