Well there Chris, the answer is, It Depends. The key word in your
question is "qualify". Often times, the document to which you are
qualifying will specify what test method, sample size, and test sample are
to be used.
Are you qualifying the cleaning process to J-STD-001? An IEC
specification? Bellcore? JEDEC? GM? EIEIO?
Or, is it in the old parlance of Mil-specs "have objective evidence on
file"?
There is no universally accepted explanation of the differences between
ECM and SIR. Both are applications of temperature-humidity-bias tests,
sort of like different flavors of vanilla ice cream.
Brian Ellis and I have debated this in the past. In Brian's view, IIRC,
was that an SIR test is one in which the resistance was monitored
periodically, with no applied electrical bias between measurement periods,
while ECM tests do have a bias applied between measurements. The newly
published revision to IPC-9201, The SIR Handbook, goes into it in a little
more depth.
From my own perspective, it really depends on what you are trying to
learn, or what you are trying to prove, and to whom you are trying to
prove these aspects. And the education level of those to whom you are
trying to prove it.
If you are trying to check off a box on a customer supplied shopping list
(e.g. fluxes are Bellcore compliant), then the tests are simple,
straightforward, relatively low cost (key word relatively). You learn
very little but the customer is happy. These kinds of standard SIR/ECM
tests use simple substrates, standard material sets, standard
environments,...... and may have absolutely no correlation to your
product.
On the other hand, test methods and substrates have been / are being
developed for IPC and IEC designed to give you very useable data on
cleaning and cleanliness for the purposes of "qualifying" assembly
processes.
Doug Pauls
Chris Schaefer <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
01/10/2008 05:02 PM
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[TN] ECM or SIR - What Electrical test is best?
Techneters,
I am having to perform some tests to qualify the wash process using an
alternative cleaning chemistry and would like to know what the real
differences are between the ECM and SIR tests besides the time it takes to
perform the test measurements.
Thanks Much,
Chris
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