Ken, I have read a number of other responses to your question and agree with most of the responses, especially Graham Anyone who desires to use an ionic contamination tester should first read an EMPF report RR000013, titled "An In-Depth Look at Ionic Cleanliness Testing". This report covers all the major models available at that time (1993, I think) and looked at them for repeatability and accuracy. That report can be obtained from EMPF at 317-655-3673. They may also have a request form available through their web page (www.empf.org). That report generally found that the units had a severe lack of repeatability, both from machine to machine, or even consecutive serial numbers of the same model. Another conclusion was that the equivalence factors, used to compare results between the different kinds of testers was largely fiction (my paraphrase). These testers can have a place, that for which they were designed - process monitoring. They were not designed as analytical equipment. They were not designed with water soluble fluxes or low solids fluxes in mind. They should not be used to determine if a process is acceptable or unacceptable. Graham Collins response regarding the blind use of these instruments by people who never seek to understand what the measures and responses indicate, was right on. I could not agree more. I have lost count of the number of my customers who have problems with corrosion, metal migration and electrical leakage, yet claim it could not possibly be ionic contamination because their ionic cleanliness tester showed levels under the 10 microgram limit. If you desire to implement such a device into your manufacturing scheme, then I would recommend that you do some studies to benchmark your response using ion chromatography and your instrument. Ion chromatography can give you a better indication of acceptable or non-acceptable (because it is ion specific) in a competant analysts hands. This information can be used to help set a realistic process control mean and limits about the mean. Forget the historical ionic cleanliness pass-fail limits, unless you are still doing high solids RMA processes. If you have an "8" on Monday, Tuesday, Wednesday, but a "15" on Thursday, something changed and you better go find out what it was. While I see great abuses of these machines and would like to see them go away (eventually), they are one of the few process control tools available to assembly personnel that work in real-time. But you need to understand what they can and cannot do or you are wasting your time and signing on for ulcers. Of course, if you like ulcers....... I agree with Graham Collins remarks about the periodicity of testing. If you have a process that is well under control, then SPC methodologies indicate you can decrease the frequency of sampling. I would not eliminate it totally though. To do so would mean that you assume the following: the laminate never changes the solder mask did not change lot to lot (the vendors would NEVER do that to me) the solder mask cure process is always perfect and gives me perfectly cured the boards from my fabricators always come in squeeky clean nothing else changes in my process There are some huge pitfalls waiting for you if you make these assumptions. Changes in ionic cleanliness readings can be a way to catch problems that occurred upstream in your process. Hope this was helpful. Doug Pauls CSL ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################