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What is the std Resistivity for DI water at Aqueous

Yngwie

#7495

What is the std Resistivity for DI water at Aqueous | 31 July, 2001

What is the industry standard specification for Resisitivity monitoring at aqueous cleaning?

What would be the diff. between specs. for normal PCBA vs PCB that has to go through wire bonding after SMT for COB process.

pls advise..thx

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Michael Parker

#7502

What is the std Resistivity for DI water at Aqueous | 31 July, 2001

Maintain DI water to 18 Meg Ohms resistivity. You can go down as low as 2 Meg ohms, in a pinch, but I would caution on what type of board you are running if trying to clean on 2 Meg ohm. Anything that is running an RF or high frequency circuit could have residual surface current creep with ionic contamination present. an older design (primarily through hole and solid digital design) could be safely rinsed in a lower resistivity rinse.

As for cleaning for COB - keep the resistivity at or near 18 Meg ohms.

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#7510

What is the std Resistivity for DI water at Aqueous | 31 July, 2001

There is no the industry standard specification for resisitivity monitoring at aqueous cleaning. Beyond those posted here earlier by Mikie, guidelines can be found in the fine SMTnet Archives, for instance: (http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=6832). Continuing with recent comments on a flux res thread, the issue is not the cleanliness of your wash water, but the cleanliness of your boards after you ship them to your customer. Yano, a biomed device will have far different cleanliness requirements than a talking furball.

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