omega meter

The EMPF has a great Paper regarding the Omega meter. www.empf.org (Click the Tech Pubs Icon) Here you will find a host of technical papers. These papers were relevant in their time but most have proved to be irrelevant in current day manufacturing. Though most of the articles are dated between 1988 and 1994, the 1 I know is useful would be Tech Pub #RR0013 An In-Depth Look at Ionic Cleanliness Testing.

I am sure Dave F will have some more technical information for you

Best regards, Cal

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Using an Omega meter to measure no-clean residue is an ineffective measure of your process for several reasons. * Resistivity of Solvent Extract (ROSE) or to use the Eurolander equivalent, Solvent Extract Conductivity (SEC): In my view, this form of ionic testing has limited utility, except in the hands of a very experienced operator, when trying to troubleshoot a process problem. * Your meter is �calibrated� to a 1970s rosin flux measurement of LT 10.07 �gm/sg in NaCl equivalent. * Rose testing washes soluble residues from your board with a DI water / IPA solution and measures the halides in the wash solution.

Ion chromatography and surface insulation resistance are two other measures to consider. Personally, if I had a choice between ionic contamination testing and SIR testing (assuming both competently done), I would choose the SIR testing as the bottom line of whether a residue was harmful. * Ion chromatography is a good tool for determining what residues are present and in what amounts, but does not answer the "so what" question. => �What does 5 micrograms of chloride mean to me?� * With SIR testing, you can show no detrimental leakage currents under humid conditions, no corrosion, no metal migration, which are the big factors in figuring out electrochemical reliability. People often have a greater comfort with passing SIR than they do with passing ROSE tests. Of course, SIR testing takes a while.

Actually, it is best to do both ion chromatography and SIR at the same time so you can determine the correlation between SIR performance and cleanliness levels for troubleshooting the process later.

Look at: * TP-1114 - The Layman's Guide to Qualifying a Process to J-STD-001. Originally developed for J-STD-001B, it is also applicable to current assembly standards. Electronics manufacturers are faced with the difficult task of proving that a candidate manufacturing process can produce acceptable hardware, either to the customer of the product, or for internal quality control. Users have to determine many of the process qualification steps on their own. This document leads you through the task of qualifying a candidate process to J-STD-001. Not available in electronic format. 13 pages. Released January 1998. * TR-582 - Cleaning & Cleanliness Test Program for: Phase 3-Low Solids Fluxes & Pastes Processed in Ambient Air. This document details the test procedures, test results and team conclusions for the IPC Cleaning and Cleanliness Testing Program, Phase 3, Low Solids Flux in Ambient Air. This effort has been part of a multi-stage program to investigate material and process alternatives to the use of chlorofluorocarbons (CFCs) in electronics manufacturing. This Phase 3 effort has been dedicated to characterizing the cleanliness aspects of low solids fluxes, sometimes referred to as "no-clean" fluxes. Not available in electronic format. 163 pages. Released November 1994.

Finally, search the fine SMTnet Archives. They contain some pretty good background on the topic.

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