Hi Cormac - There is a very big difference between metal oxides and metal salts. They are not the same ionic species and react differently to in SIR testing. Metal oxides do not dissolve during SIR testing - electrochemical processes breakdown oxides. Metal salts can be dissolved. I suggest contacting Doug Pauls ([log in to unmask])- he is heavily involved with the IPC SIR committees and can do a much better job of explaining the differences of oxide and salt SIR reactions. SIR testing is a very complicated subject and is always changing which makes it tough to keep up with. Dave Hillman Rockwell Collins [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: Re: ASSY:Ionic contamination specs Author: [log in to unmask] at ccmgw1 Date: 6/13/97 6:34 PM John, The ionic contamination the customer is measuring, is not actually being "picked up" during shipping/handling, but rather, is likely the result of oxides of Tin and/or Lead forming on the solder areas of the board. These oxides (salts) will dissolve slowly during the SIR test, raising the conductivity and thereby be measured as ionic contamination. Is the customer's contamination limit practical?. Well, if one goes by the motto that "the customer is always right", then the issue becomes what to do about the contamination. Thorough cleaning of the boards to reduce ionic contamination to virtually zero is essential and not have a situation where those boards that marginally pass the ionagraph test after washing, go on to fail at customer inspection. The cleaning solution should contain an anti-tarnishing agent that will inhibit any subsequent oxide formation. A good cleaner will remove oxides (white haze) from the laminate as well as the fused solder. Products to perform these functions do exist. Please contact me if you have any further questions or comments. Best regards, Cormac Kissane Technical Service Representative RD Chemical Company [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************