Terri's - point are well taken. To steal a phase from the real estate
industry, what is very important is not only type and quantity of ionics
but "location, location, location".
I'd also like to refer the forum readers to Steve Shoda/BAE Systems
paper from 2007 APEX. It's posted on the IPC website in the members
section.
It does the best job I've seen to date, attempting to correlate the
various ionic test methods to one another.
For those of you that are not familiar with it, its well worth the read.
Rich K / Kimball-GTS
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Terry L. Munson
Sent: Tuesday, February 19, 2008 1:25 PM
To: [log in to unmask]
Subject: Re: [TN] cleanliness testing
Graham
I agree with Bev, but to better correlate the issue to performance.
Subject
the assembly to a non condensing high humidity biased (functioning)
environment (40C / 90%RH can work) and functionally assessment after
this exposure and
then determine which part of the assembly is having the performance
problems. This gives a performance parameter that is compared against
the Ion
Chromatography in specific area extractions. This can tell you much
more about the
residue under an 0201 or in the SMT area next to a hand solder (or
selective
solder) location that trapped heavy flux but was poorly cleaned.
Averaging
the total board is a 10,000 ft view of the PCB cleanliness and process
effect
but looking at the critical areas of the circuit such as resistor
network,
RF filter, or capacitor series on critical circuits can tell you how
much
contamination is needed to create a problem or perform well. If you
could use a
localized extraction system that assessed the residue effect under
electrical performance and then analyze the amount of ionic
contamination by IC, this
would give you an indication if the residue was corrosive or not based
on
some defined criteria. But to say that a board is clean or dirty by the
general
ROSE testing is difficult with today's assemblies and chemistries.
Terry Munson
Foresite
765-457-8095
In a message dated 2/19/2008 12:37:37 P.M. Eastern Standard Time,
[log in to unmask] writes:
Hello TechNet
I'm in a debate with a supplier about the incoming cleanliness of one
of
their parts, they claim it's squeaky clean and I claim it's as salty as
a bag of
salt & vinegar potato chips. Obviously we are both exaggerating, but
one of
us has a good claim.
They are fending me off with resistivity measurements made per the
manual
test method IPC-TM-650 2.3.25 - which works in that I don't know how
to
convert it to the "ug NaCl/in2" equivalent units I'm used to. Is there
a valid
conversion?
Sir Doug of Dew, if you reply please do NOT say it depends...
regards,
Graham Collins
Halifax Production Engineering
L-3 communications Electronic Systems
(902) 873-2000 ext. 6215
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