Hi Graham,

Take a look at the latest revision of IPC method 2.3.25 rev C.  It describes 
how to make the conversions from resistivity to ug of Na/Cl equivalents / 
sq. inch under section 4.4.  You will need your supplier to provide you with 
the calibration curve of the bridge probe they used on the day that the test 
in question was performed.  In addition, you will need the volume of 
solution they used.  Also, if you don't have this method you can find it for 
free at IPC's website. Go to Knowledge, then Standards, then TM-650 test 
methods download page, then section 2.3 chemical tests. I hope this helps.

Best Regards,

Joe Russeau
Precision Analytical Laboratory, Inc.

----- Original Message ----- 
From: "Graham Collins" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, February 19, 2008 12:35 PM
Subject: [TN] cleanliness testing


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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