Greetings from sunny Arizona: This is my first posting to the net so bear with me a bit please. I recently had the question posed to me "we have a concern about the possibility of autocatalytic corrosion in vias due to residual RMA flux activator due to tenting of one side of the vias; what corrosion rate might we expect". I am familiar with the term "autocatalytic corrosion" as it applies to crevice corrosion in stainless steels exposed to aerated chloride solution. This is where chloride ion diffuses into the crevice and is regenerated as freshly generated metal chloride hydrolyzes to chloride and insoluble metal hydroxide. As chloride concentration increases so does corrosion rate. Apparently this can also occur in copper and other metals. I don't think this is the case with via corrosion since the chloride concentration is fixed. My approach was to assume the activator is diethylamine hydrochloride, which I assume hydrolyzes into hydrochloric acid. I also assumed that the acceptance limit of 1.55 micrograms per square centimeter NaCl equivalent (MIL-STD-2000A) was the coverage within the via. I next assumed that the via was filled with rinse water and that 99.5% of this water evaporated. This left (fortuitously) 0.1N HCl in the via, for which Uhlig and Revie happen to give an initial current density for copper electrode of 2E-3 A/sq meter. I assumed this rate of reaction remains unimpeded (i.e., no polarization) and calculated time to penetrate 4 mils of Cu. I got about 20 years. I must admit that I assumed NO amine-caused stress corrosion cracking and no other fast reactions. Does anyone have experience or alternate analytical approach? ################################################################ 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 ################################################################