Doug,
I would be most grateful if you could send me a copy of your cleanliness
narrative as well (in fact you may get swamped with requests for this).
You've hit the proverbial nail by saying we know boards need to be clean,
but just how clean and how do we tell has always been one of the world's
mysteries that I have been able to leave to others inthe past.
I am now having to spec a small cleaning system (DI water for preference,
but we have this old solvent cleaner that the bean counters would like to
try and resurrect if possible). I am largely running by guess and by God as
to the cleanliness levels I want the machinery to be capable of, but what
the best method of measuring the end result is, I have no clue. ANy help or
pointers are most welcome.
Peter
[log in to unmask] 09/08/2002 08:18 PM
Sent by: TechNet <[log in to unmask]>
Please respond to "TechNet E-Mail Forum."; Please respond to dopauls
To: [log in to unmask]
cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Subject: Re: [TN] Board cleanliness
Patrick asks:
I would like to know how to specify board cleanliness on the Fab drawing.
We use
class 3 boards. Does it make any difference on cleanliness standard? Is it
OK
to ask for cleanliness test results/reports shipped with every lot? Which
department in a company should be responsible for this board cleanliness
issue,
R&D, Quality or Production?
Thanks in advance to everyone sharing this information.
Doug answers:
Patrick, I chair the IPC Bare Board Cleanliness Assessment task group, so I
will take a shot at answering your questions. Other than my stock answer
of "it depends", the questions can be kind of complex, depending on
volumes, your capabilities, and your pain threshold.
Many people are in your position. They know that board cleanliness is
important, they know present measures are not worth that much, and they
don't know how to do the wording in the purchase specs. To assist people
in that position, the committee (well, pretty much me, but no one has
argued yet) put together a narrative. It has never been released as an
official document, but was intended to be a tool for the IPC staff to give
to people like you who ask the questions. The text does not translate well
to an e-mail message, but I can send it to you separately if you like.
For class 3 boards, I consider the current IPC-60XX series requirements as
inadequate. Back in 2000 (October if I recall) I wrote an article for the
IPC Review looking at all the available bare board cleanliness specs. The
requirements do not change by class numbers. They all say the same thing,
10 micrograms NaCl equivalence per square inch. If you have a board that
is that dirty, pack it in. It will never survive.
Is it OK to ask for cleanliness on every lot? It is always OK to ask. But
be ready for the return questions. By what method? Why do you need them
this clean? How much extra are you going to pay me to provide the
draconian amount of data?
Which department is responsible? Whoo boy, that's a good one. I would say
that it is the responsibility of your R&D department, together with your
engineers who do accelerated life testing, to come up with a figure for how
clean your hardware has to be, and by what measures you use for clean.
Once you put the test method and criteria in your purchase document, it
becomes quality's job. Just make sure that you establish a good
correlation between the vendor test data and your internal test data for
the same test.
I could go on and on and on......... but this serves as a start.
Doug Pauls
Rockwell Collins
---------------------------------------------------------------------------------
Technet Mail List provided as a free 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/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
---------------------------------------------------------------------------------
---------------------------------------------------------------------------------
Technet Mail List provided as a free 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/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------
|
