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SIR Testing

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SIR Testing | 4 July, 2006

Calling for an input from the Experts our there.

Our customer is questioning the cleanliness of the no-clean product that we produced for them. We were asked to clean the board (localised cleaning) after rework (IC need to be changed due to an up rev.). Excessive touch up flux spreaded on the board plus bad localised cleaning (using IPA)has caused rejects cosmetically. This has been rectified, but about 200 boards were done badly.

Customer is asking from us one fresh loaded board and one localise cleaned board for them to do the SIR test. This is the actual production board with the finest pitch of only 25 mils.

My questions: Can this board be used for SIR test? Is using the actual board be more accurate for SIR testing (even without the comb pattern like those on IPC-B-24)? If so, how to go about with the bias voltage 50V inputs? What is the SIR value we will take as a reference?

Appreciate any input and thanks in advance.

Rgds. Mustang

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SIR Testing | 4 July, 2006

I had a couple of reps in from Indium a few weeks back, and they were promoting a flux for rework that was designed to have low SIR, No clean. Havent tried it yet. The product is Flux NC 771, might solve your problem? Regards Slaine

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SIR Testing | 4 July, 2006

The heat from a soldering iron will push raw flux across the surface of the board and into surprising places. It's bad practice to squirt liquid low residue flux on the board during rework, because the portion of the flux that does not get heated properly by the soldering iron is corrosive. Consider getting the boards cleaned by a professional.

You're correct. SIR testing can only be done a a board designed for that purpose. It will have a comb pattern, like the one you mentioned, somewhere on the board, usually hidden. If the board was not designed with that purpose in mind, a process can be validated with a board designed for testing, like the IPC-B-24.

Is it possible that your customer was thinking ion chromatograph, but saying SIR?

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SIR Testing | 4 July, 2006

Thanks for your fast respond Dave & Slaine. It was much appreciated.

Dave, I'm not familiar with the ion Chromatograph testing i.e. how different it is versus SIR, but you could be right. May be they have mistaken this. Let me try to search for some information that are available in the previous SMTNET thread to understand what exactly ion Chromatograph is.

Thanks again.

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SIR Testing | 5 July, 2006

IVF Research Publication - "Cleanliness and Reliability: Evaluation of Test Methods and the Impact of Contamination from the Production Process on the Reliability of Printed Circuit Board Assemblies"

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SIR Testing | 6 July, 2006

Ionic Cleanliness Testing: IPC-TM-650, Test Method 2.3.25, Section 5, "Dynamic Extraction Method", is the most commonplace method in the industry to test YOUR PCBA's for cleanliness. Run it through your process as normal, and send it out for testing to an independent lab.

SIR Testing, as Mr. F states, utilizes a special board with copper traces (comb-up pattern). In my past life, I've ordered these boards directly from IPC, ran them through my process, and again, sent it out to the lab where they did perform actual SIR Testing.

Most paste and flux manufacturers provide Telcordia (Bellcore) SIR Data in their technical literature. You can take their word for it and use it as documentation to provide to your customer.

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