There are two primary equations that I know of. The first is more of a rule of thumb and is based on an Arrhenius rate of reaction. The second, which is recommended, is the Eyring Model. The IPC SIR Handbook (IPC-9201), which is nearing publication, has a section detailing this equation. It can also be found in the original report of the Low Residue Soldering Task Force. I don't think it will come across well as an ASCII text message. If you will give me a fax number or mailing address, I can send you the necessary references. Doug Pauls CSL [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************