Hi Kathy, Water sol fluxes are *INDEED* ionic materials and can/will cause serious reliability problems if not thoroughly removed. Surface resistivity (also known as SIR or Surface Insulation Resistance) is a good "localized" test as a special layout (opposing interlocked comb patterns) must be present on either the assy or a coupon. These are not always practical for production as PCB real estate value increases. ( Doncha' wish Calif real estate value followed suit?!) This test is a good barometer for process qualification and localized evaluation, such as underneath micro-BGA, etc. The more common method for production is the solution extract method commonly known as "Omegameter" or "Ionograph", depending on the manufacturer of choice. I know of a few good used machines in the area if you're interrested. This method essentially starts with de-ionized water-alcohol solution then the assy is immersed for a period (typical 10 min) so the contaminants dissolve into the solution. The volume resistance is then measured and based on the volume of solution and surface area of the assembly, one can determine the ionic residue in terms on micrograms of nacl per sq. in. Typical industry standards for high quality commercial product is 14 micrograms/sq. in. The reason nacl (salt) is mentioned is that the test is not selective, but is an equivalent conductivity (or resistivity) to salt, which the effects can be readily quantified. The drawback of this method is that it will not identify a potential problem in a "trouble area" such as underneath a daughterboard because it averages the results over the entire surface of the assembly. It is, though, a reasonable "barometer" *IF* in a case of a known potential trouble spot, SIR was done to first determine the effectiveness of the cleaning process and further correlated to Omegameter measurements for prodution confirmation. I can help you set up these tests in house and would love to stop by to discuss it with you. Regards, Ed Popielarski QTA Machine 10 Mc Laren, Suite D Irvine, Ca. USA 92618 Ph: (949)581-6601 Fx: (949)581-2448 E-Mail: [log in to unmask] ################################################################ TechNet E-Mail Forum 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://jefry.ipc.org/forum.htm) for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################