In a message dated 11/11/98 9:39:24 AM Pacific Standard Time,
[log in to unmask] writes:
<< Does anyone know if there is a test lab in San Jose,CA which can test
for the ionic contamination level on assembly?
Also do you think I should use the 10.06 mg NaCl/ in^ as the limit for
a no clean process?
Thank you for reading this mail >>
Hi Rudolph,
I don't think you really want to use an ionograph to check for
contamination in a no-clean environment in the same way it's used in a
cleaning environment. Ionographs are good to check your incoming material to
be reasonably sure you're getting clean stuff to begin with, but it won't be
able to tell you what harmfull contaminates are introduced while you're
putting it together. That's why it's so important that there's a "no-clean
mentality" with everybody on your production floor, from stockroom personel to
your machine operators. Everybody has to practice the proper habits while
handling the parts, pcb's, and other material so you don't introduce the ionic
contamination that normally get's washed off going through the cleaners.
If you still want to get the level of ionic contamination on the boards
measured, you might try calling KR Anderson. There was a demo Ionograph there
that you could get a test done if you wanted to, but you would have to listen
to the sales pitch to buy an ionograph from one of the Alpha reps
though...which is pretty painless B^}. But since Cookson has taken over the
whole enchalada and created their "Speedline" group, they may have moved the
machine out of KR Anderson over to their new place off of Lafayette in Santa
Clara (kinda' over by 3COM).
One other thing to think about as well, just because a board passes an
ionograph, it doesn't mean that it won't fail down the road due to some sort
of contamination. There's a number of other harmful contaminates that won't
even show up in a ionograph.
My humble opinion is that you should send your boards to a lab and get a
Surface Insulation Resistance test done to see whether or not you're building
a clean product. (It should have been one of the tests done to qualify your
no-clean paste/flux).
There's a number of Labs in the Bay Area that can perform those tests for
you, but they not be cheap! They take 7-days to complete for class-2 product.
All the parameters for the test are spelled out in IPC-TM-650 Test Methods
Manual, number 2.6.3, Moisture and Insulation Resistance, Rigid, Rigid/Flex
and Flex Printed Wiring Boards.
Most shops that perform these services are familiar with the parameters.
There's one shop of I know called Quanta Laboratories that charge $125 a day
for small boards (less than about 14" X 14") and it goes up from there for
larger boards. You see, once the test has started, the doors to the chamber
can't be opened, or the test interrupted, until it is finished for it to be
valid...that's why the BUCKS! Quanta Labs can be reached at (408) 988-0770...
they're over off of De La Cruz Avenue over by San Jose airport.
You might be better off getting your own S.I.R. chamber...I imagine after not
too many tests at a lab somewhere, you coulda' probably paid for your own
chamber (pretty quickly too) If you plan to stay no-clean, you'll always have
a need for it.
Well, it's time to go home and take my weekly shower, so I can get all the
contaminates offa' me and not electromigrate...(can ya' believe it? It's not
even Saturday!)
-Steve Gregory-
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