I think that it is really important to remember that using IC testing will
measure your process capability and is a tool to verify that your process
is in control. IE that you are not adding any contaminants to your board.

*One valid use for IC, yes, but I would say more of process consistency
rather than process capability.

I disagree that the numbers CSL or IPC 610 has come up with mean anything
though - if you tested a complete assembly and the chloride levels per cm
squared were grossly higher than a published number this doesn't really
mean that you suddenly have a problem. It means you have alot work left to
do in order to determine if there is a problem. Three months down the road
if the number is the same you can feel comfortable that your process hasn't
changed.

*I agree with most of this, but argue that the numbers DO mean something.
In my original message, I indicated that the CSL numbers are a good
STARTING point. I should have expanded on that to say that if you don't
have a clue as to what  your residue picture is now, then that might be a
good place to start.  On the other hand, if you have a process that is in
control and you are not seeing failures in burn-in or from the field, IC
testing can tell you what levels of residues may correlate to that
acceptable performance.  You then have a good idea of what is good for YOUR
hardware and YOUR end use environment.

The biggest thing I feel about IC testing is that it is like a computer, it
will only tell you what you tell it to.

It is not a miracle test and will not solve your problems for you, apply
common sense and engineering practice with a grain of salt ; )


*I respectfully disagree.  Your statement implies that you can make IC say
whatever you want it to say.  IC data, when properly generated and properly
interpreted, can be a very powerful tool for characterizing, optimizing,
and troubleshooting a process. IC is a tool.  It has valid and invalid
uses.  It has valid and invalid applications.  It has valid and invalid
interpretations.  I agree with yoru last statement that you have to use the
data wisely and not try to blindly apply numbers.

Doug Pauls

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