Hi Ted,
I wrote a response to this from work yesterday but it got hung up at the
IPC server for some reason... I am on vacation at home here, so I will
try to recap my thoughts...
This is key - The fab drawing is really the controlling document that
both you and the vendor have that sets the 'accept or reject' criteria
for the job... whatever is specified on that document is your contract
with the vendor. They must supply boards that meet that criteria or they
do not get paid. They go into it with that knowledge when they bid the
job. They know full well that if they fail to meet the requirements of
the document they will be getting back rejected materials. That being
said....
You as the responsible designer also have to weigh the importance of
meeting schedules, and meeting the product requirements, a contact you
have with your customer... very similar to the one you have with your
board shop. If you don't produce product that meets your customer's
needs, on time, you will be getting back rejected materials... and no
money. :( nobody wants that.
SO... here's the deal. If board shop 'A' decides to deviate from the
drawing... they are in effect taking the risk that you won't reject the
materials due to non-conformance. (You'd be surprised how much of that
sort of thing goes on all the time and mostly it's due to
miscommunication.) Most good board shops are wise to this problem and
get on the phone right away to get a clarification of your
requirements... they don't want to get the shipment back instead of a
paycheck either...
The assembly house, in your situation has a big responsibility. If I
read your story correctly, they have 'subbed' it out to a board vendor
right? So in effect you have allowed them to broker or handle the board
fabrication AND assembly correct? If that is the case, they are
responsible for reviewing the fabrication drawings and making sure their
tooling will be able to handle the assembly panel design or they need to
change it to conform to their tooling... which it sounds like that may
be what they did. Granted they should have spoken with you or your
company's buyer... but I bet the PO for the job only states that you
want finished assembled boards in de-paneled form... If they were
negligent in their handling of the sub out process, I don't think you
should have to absorb their excess costs... That was their in house
issue and they should absorb it.
In the CID workshop we try to emphasize the importance of
documentation... it must spell out ALL the requirements of the board,
including assembly panels. Anything you leave to interpretation 'can and
will be used against you'... etc... etc... if you know what I mean. I
can't stress enough the importance of complete dimensioning of tooling
and mechanical interface holes, cutouts, layer stack up and
tolerances...and details for the assembly panels. I personally have been
bitten in the past by leaving the board vendor too much 'freedom' to
choose how something is done and ended up having to make our boards in a
more expensive manner... or having the boards come in need of rework or
even un-useable. You as the designer need to check with whoever is going
to build your boards and assemble them to make sure that the panel
design meets all their tooling needs... then get them to sign up to it.
OWNERSHIP of the design is very important... don't relinquish it to
anyone else. It's your design, see to it that all the details are
specified and you know what the end result will be. Some of us have been
a bit lazy in the past and we tended to 'boiler plate' the notes or
details and tried to reduce our own workload in documenting the job, and
we got away with it often because the board shops we used reviewed the
job and 'fill in the blanks' for us... they WANT to serve us... but we
expose both our companies and the board vendors to risk if we don't nail
it down and put the details into the 'contract' or fab drawing up front.
All of us need to pay more attention to the content of our
documentation, I have seen so many board vendors complain of the same
issues, details overlooked, dimensions left off, notes that do not apply
to the board, soldermask, finishes, stack up details... Some of us fall
into that age old trap of hooking up the last line and saying to
ourselves... I'M DONE! ... well, like the old saying, its not done
until you do the paper work... don't forget someone else is going to
have to build it and they can only go by how well you communicate the
requirements to them. And your inspectors can only reject boards that do
not meet your requirements if you have documented them... otherwise how
can they reject them?
Now that I have said way too much... This doesn't get the board shops
off the hook either... they need to open the lines of communication to
the designers as well... not just 'guess at' what the designer meant...
It surprises me how many times I have seen boards come in that are
nothing like the print... it's like they think they have ESP or
something and think the designer will understand if they 'change this
one thing' that makes their job easier... STOP... CALL... don't assume.
Often the designer knows exactly what he or she is doing... and they did
it that way for a good reason... talk with us... we are nice people
really! We might be able to explain it and then we both win...
I have heard that there are lawyers that make a living dealing with
settling company lawsuits over design related miscommunications... so,
to all of us, be careful and protect your company by making complete
documentation that cannot be misinterpreted... and communicate,
communicate, communicate.
Happy holidays and Happy New Year folks... :)
Bill Brooks
Printed Circuit Design Engineer, C.I.D.+, C.I.I.
[log in to unmask]
http://www.dtwc.com
http://dcchapters.ipc.org/SanDiego/
http://pcbwizards.com
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Ted
Tontis
Sent: Thursday, December 30, 2004 7:10 AM
To: [log in to unmask]
Subject: Re: [DC] Assembly panels
I understand that the IPC documentation is a guideline, but when
I sent the drawing package out to the assembly house I was told that
there wasn't a problem. I even sent out a .PDF with the dimensions of
the assembly panel weeks before I sent out the drawing package. I was
told by the assembly house that the panel was fine. This is not the
first time this has happened, (changes have been made with out first
contacting us). It cost my employer a good chunk of change. I wasn't
part of the design team on that project and had no real knowledge of
what really happened until yesterday. We contacted the assembly house
(they sub out the boards) to confront them on this issue. I hope that
conversation will force the doors of communication open.
Thank you for your input,
Ted
>>>>
Hi Ted,
The IPC Documents are intended to be guidelines. While you may have
drawn the panels perfectly per the IPC documentation, many fabricators
will panelize per the size of panel that they need, the optimum use of
the material, and the material size they have on hand. This is intended
to save you money. While you are correct to be concerned about any
changes that are made, this was probably done by the fabricator rather
than the assembler. They should ask before they do it, but some shops
don't. Why don't you ask them for documentation as to what all changed
and inspect that documentation carefully.
And definately talk to your fabricator and assembler. While the IPC
documentation is the perfect place to start, it is not the only correct
way to do things. The shops may both be able to explain any changes they
made and why, and give you guidelines that you can use for your future
reference with those shops. Also explain your concern to them that no
changes ever be made without your permission.
Good luck,
Susy
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