Mary,

Are you sure you mean 2 mg/sq. in. or do you mean 2 mg/sq. cm? Even Bell Corp allows 7 mg/sq. in. I'm not sure a bare board supplier can maintain 2 mg/sq. in if any type of soldermask is used. This is a very tight requirement. If you specify this requirement, I would recommend adding a statement such as " when tested in accordance to .....". This will specify the type of testing required and eliminate any potential correlation problems in the future.  There is a variation in results based on test method. The most recent issue I had to deal with stemmed from my not using a heated solution vs my customer using a heated solution.

If you stipulate an LPI, I don't think you need to specify a brand. As for as test method, specify the same method and chemicals you intend to use to verify the parts at receiving.  Once you have stated the requirements and test methods, the supplier should be able to choose a mask that will meet those requirements . Just my thoughts. 

Ed Cosper
Director, Quality Assurance and Engineering
Graphic Electronics Inc.

----------
From:  Davis, Mary[SMTP:[log in to unmask]]
Sent:  Monday, March 03, 1997 2:04 PM
To:  TechNet
Subject:  No Clean Bare Board Controls

I would appreciate some guidance on a subject that could be of interest
to others in the same dilemma.

We are specifying controls for unpopulated PWB's to be used in low
residue/no clean process.  We plan to restrict bare board bulk ionic
levels to no more than 2 micrograms/sq.in. NaCl equivalent.   Also, it
has been suggested that we require that 'polyethylene glycol substances,
as well as certain dry film and even some liquid photoimageable masks be
avoided'.  The bulk ionic requirement is easy to communicate but I am
struggling with the verbiage and test methods that describe restrictions
on polyethylene glycol substances and other potentially harmful
materials. 

Any help in this matter will be greatly appreciated.

Mary Davis
Sr. Material & Process Engineer
Hughes Aircraft
Naval & Maritime Systems
206-356-3311
[log in to unmask]



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