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Effects of Silicone on Ionic Contamination Testing

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Effects of Silicone on Ionic Contamination Testing | 17 October, 2013


We are building a CCA which has a silicone-based adhesive whose purpose is to bond the bottoms of multiple LED displays to heat sinks. Our customer wants the CCA to be tested for ionic residues per J-STD-001, but we are hesitant to test the CCA due to this silicone.

Our facility uses an Ionograph 500M for ionic contamination testing. Our factory's testing prodedure forbids placing a CCA containing silicone into the test cell, since the silicone will contaminate the test solution. I cannot find any information on why this happens, however.

Can the presence of silicone on a CCA ruin an ionic contamination test system? If so, is it even possible to test this CCA?

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Effects of Silicone on Ionic Contamination Testing | 18 October, 2013

You might try testing prior to using the Silicone if possible. Also you might try to qualify your cleaning process rather than the individual board. Clean an unrelated assembly and test it in your Ionagraph. Assuming it passes, Clean your subject assembly, but do not test. Then clean another unrelated assembly and test it. If it passes you could reasonable say that your cleaning process removes ionic contamination, and that the subject board would be free from contaminates. I don't know, however, whether silicone in its cured form can emit or present ionic contamination in and or itself. Just an idea... 'hege

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Effects of Silicone on Ionic Contamination Testing | 22 October, 2013

Dear Lord,

We have had similar challenges with customer requirements related to ionic testing. You have determined that you cannot get a reliable result from testing at the stage where the adhesive has been applied. That option is out.

Assuming that Hege's logical plan wouldn't fly with your customer, here's what I would do:

1. Figure out where, upstream in the process, you can perform the cleanliness test to get a reliable result and generally be representative of the assembly process (most components installed).

2. Do an assessment of what risks downstream processes pose in adding/creating ionic contamination to the assembly.

3. Mitigate those risks. This may be done through mandating use of nitrile gloves for handling, review and update of manual cleaning process, etc.

4. Present to your customer as "This is what we can do to meet your requirements." not "Can we do this....?".



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