Thanks for posting that.
...very well-reasoned.
Guess I was feeling like a mother hen,
didn't want the shouting to scare
anyone away from participating here.
(like that's really my job)
sorry about the decaf comment,
Jack
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| | JaMi Smith |
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| | DesignerCouncil |
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| | rv.ipc.org> |
| | |
| | |
| | 06/09/2003 02:40 PM |
| | Please respond to |
| | "(Designers Council |
| | Forum)"; Please respond|
| | to JaMi Smith |
| | |
|---------+---------------------------------->
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|To: [log in to unmask] |
|cc: |
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| Subject: Re: [DC] Core thickness/emissions |
>---------------------------------------------------------------------------------------------------------|
Caterpillar: Confidential Green Retain Until: 07/09/2003
Retention Category: G90 -
Information and Reports
Jack and others responders.
Let me first say that my responses to this thread are based on a few
assumptions, or should I say more correctly presumptions.
Reading the original post I made two assumptions.
1.) The original poster, due to his or her title, was in a position that he
/ she knew, or should have known, that the PCB had been previously built
and
and that the product had already been thru emissions testing.
2.) That the person at the board shop knew, or should have known, that the
board had been previously built before, in the same form factor and exactly
as specified, and that the order for more boards was an order for a follow
on build or production run.
Maybe I am wrong on one or both of these issues, but they both seem pretty
obvious to me from the fact that the board had already tested for emissions
(even though the guy at the board house possibly did not know this
initially, although it reasonabally seems that he may have found that out
somewhere in the ensuing dialogue).
Usually, once a board has been tested for emissions, it either needs small
modifications to fix a problem, which would be followed up by a small batch
of boards and retesting, or it is approved, and it is followed up by a
production run.
While once again I will point out that my response was based on
assumptions,
it seemed pretty obvious to me, based on the content of the original post,
that this was a situation where the board had already been previously
built,
and the circumstances dictated that everyone involved knew that the board
had been previously built.
That is why I say that the guy at the board house blew it and blew it
bigtime.
Yes I know that on a first cut of a board, that the guy at the board house
is going to possibly ask anyone whether or not he can change the stackup of
the board to meet his favorite build and all of the materials that he has
leftover from his last project.
Yes, we have all seen this, but we also all know that you can pretty well
tell by looking at a layout and specifically by looking at the stackup
specification, whether or not the stackup really matters or is critical in
a
specific design. Anyone with more than a few months of experience in a
board
house can probably tell by looking at gerbers and noticing that there are
different thicknesses on certain traces, that they have a high speed or
controlled impedance design on their hands. All of this is pretty obvious.
No, I don't think that it is wrong for him to ask if the stackup can be
modified, but where there is a detailed and specific stackup called out on
the fab drawing (again, being presumptious, I feel that there was in this
case), then I believe that the guy at the board house needs to be capabile
enough to recognize that it has been thought thru and specified for a
reason. For some reason in this case I don't believe that the guy at the
board house was either smart enough to see this, or that he saw it and
didn't think it thru himself.
Forgive me for being presumptious, but once again, based on the assumption
that it was a return order for more boards that had already been built, and
also the assumption that there was a specific callout for a specific
stackup
that in and of itself answered the question before it was asked, I will
once
again state that I think that the guy at the board house was an idiot and
incompetent.
Considering the company that we are dealing with here, I also made some
further assumptions along the lines that the board house knew or should
have known that when they asked for something, it was becaused they
specifically wanted it that way.
I guess what I am saying here is that it is one thing for the board house
to
say "Are you sure that you want to build it with this stackup?" on the
first
pass of a board, but that they should never try to impose a change on a
stackup that is well defined (which to me it sounds like they did in this
case (again, possibly presumptious on my part))
Additionally, I can't really fault a board house that might also point out,
even on a follow on production run of an existing board, that a production
run might be much cheaper if the stackup was changed to thus and such, but,
at the same time, I would insist that it is the responsibility of the board
house in this situation to point out all of the ramifications of such a
change, and further, make sure that all of the ramifications were
completely
understood all of the way down the line (which does not appear to be the
case here). If this board house actually did this in this case, I believe
that they would have learned somewhere along the line that the board had
been through emmissions testing, and at that point, the board house itself
should have pointed out the obvious and reversed their own position, and
told the designer (manager?) and the engineer, that any changes would have
invalidated the testing. And yes, I do believe that it is the
responsibility
of each and every board house, and each and every employee of that boatd
house that is in a position to "reccommend a change" to a stackup, to
specifically know that.
The initial post simply pushed my buttons, in that it really appeared to me
that the guy at the board house really didn't know that, and futyher that
he
didn't have his eyes open enough to see what he had in front of him, or he
didn't really understand what he had in front of him, or worse yet, he did
understand it and was just trying to make his job easier or push some
excess
material.
Maybe I was wrong in this particular instance (although my gut feeling
still
tells me I am not), in which case I owe the specific individuals here an
apology. However, this happens all to often in our industry, and there are
far to many people out there in board houses causing this kind of problem,
and this needs to be discussed, yes even to the point of "dumping" on
people
and calling them an "idiot" or "incompetent".
I have no real idea of how many of the PC boards that are designed and
produced in this industry are specifically going to end up in products that
are either UL - FCC certified, or CE - CISPR certified, but I would venture
to say that it is at least 50 percent.
With very very few exceptions I would say that you should never under any
circumstances change a board that has been thru emissions testing.
Notwithstanding the legal issues involved (which say that you can't make
any
change without retesting), most, if not all engineers who understand
emissions and emissions testing would probably agree with me on this point.
I would even go so far as to say that for many if not most companies in our
industry (and I think that it is pretty obvious to most people just who
those companies are just by the products that they manufacture and in many
cases just by their name), with very very few exceptions that you should
never under any circumstances change a board that has been thru the
prototype cycle and is in a production run.
If you can't tell already, I think that the board house is responsible for
knowing this and understanding this.
I think that it is the responsibility of engineer, designer, and board
house
alike, to at least understand that in the world of CE certification
specifically (and all types of certification in general to some extent),
that any incompetence such as has been exhibited here, is not just
incompetence, but in the legal perspective of CE types of certifications
specifically, this rises to the level of Negligence. Legal Negligence. And
in certain circumstances, that could even rise to the occasion of Criminal
Negligence.
Yes, maybe I am being a little hard on the specific people involved here
(then again maybe not hard enough), but I am certainly not being hard
enough
on the issue.
No, I really don't think I am making a mountian out of a mole hill, just
calling a spade a spade.
Sorry to upset so many people here on this one, but I can't just let this
one go by unchallanged.
JaMi
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