Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Contamination test

Yngwie

#7448

Contamination test | 29 July, 2001

When carry out the contamination test,do we measure for Chlorides on water soluble and No-clean fluxes?

1) What is the equivalent factor for machines developed to test the board cleanliness, Omega-meter vs Ionograph vs Zero-ion. 2) What values do we specify? 3) Do we monitor Bromide levels? 4) Do we have a Bromide spec? 5) our incoming told me that the contamination test is a none value add process at Incoming. They have pushed it out to our PCB supplier to do it, you know the "leave it to them kind of thing". I don't say the Supplier cannot be trusted but, to have a better control on what is hitting my process, I think this should be carried out in-house. Do you think so ?

Pls advise.

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CAL

#7449

Contamination test | 29 July, 2001

Your Ionograph and Zero-ion Values are set by you. There is no raw pass of fail criteria only the limits you set up.

Ionograph is great for bare board resistivity (salt) test just as a pass fail for incoming inspection but this is all per your factorys set points. A technical paper that will help you out is EMPF RR0013 - An In-Depth Look at Ionic Cleanliness Testing (August 1993). This can be down loaded from the http://www.empf.org web site. This doc should be able to answer all your questions

Cal

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Yngwie

#7454

Contamination test | 30 July, 2001

Thanx Cal, how can I get the archive for year later than 2000 ? I've requested, the RR00013 but still waiting for the reply. Anyway, thanx in advance.

Do people measure Bromide ? how about Chromatography test ? can it helps ?

cheers

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#7483

Contamination test | 30 July, 2001

You should specify the level of res based on the effect of the res on the end-use of the product. J-STD-001 defines cleanliness requirements for ALL flux types, including water soluble and no-clean that you mention.

1 There is no equivalency between Omega-meter vs Ionograph vs Zero-ion. J-STD-001 specifies that when using these extraction testers there shall be less than 1.56 ugm/cm2 sodium chloride equivalent ionic res [or words to that effect]. Continuing, there is no means to compare the levels of res measured by resistivity of solvent extract, ion chromatography, or surface insulation resistance tests. Finally, extraction testers are not commonly used on NC boards, because these testers �aqueous� wash boards and measure the �saltiness�, combined halide effect, of the solvent. Oooo, oooo, one more thing; solvent extract testers are intended to process control tools that provide a relative measure. So when you see a change in the measure, you know it�s time to put on your little red fire person�s hat and leap into action.

2 Again, specify a level that will not affect the LT performance of your product.

3 Bromine is added to improve the fire retardency of your boards. [It�s the �F� in FR-4. Well actually, it makes a G-10 in to a FR-4, but that�s the idea.] It would be a good idea to limit the amount of this halogen on your board. Some in Euroland want to eliminate the use of this material completely.

4 There is no industry standard. Use the suggestion of 2 above.

5 Your incoming inspectors are correct that testing [and inspection] are zero value added, providing they have measured for contamination and never seen a problem. Further, foisted this testing off to your supplier is fine as long as they are auditing the supplier�s process and performing independent testing periodically. [After passing the testing on to your supplier, does testing become a value added process for your supplier when they charge you for performing the test? And it costs you money to audit the process, doesn�t it? So, if it costs money to pay for it and to audit it, how is it a zero valued added process? Hummm.]

Expanding on Cal�s comments, EMPF RR0013 �An In-Depth Look at Ionic Cleanliness Testing� (August 1993), while an excellent document, is limited to solvent extract testers.

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