As a general acceleration transform you can see "Soldering in Electronics" by R. J. Klein Wassink, 2nd Edition, page 216. He gives an equation for acceleration in temperature/humidity environment for corrosion of A = exp( (B*(1/T(L)-1/T(T))) + C*(RH(T)^2 -RH(L)^2))) Where A = Acceleration Factor B = ~7000K, equivalent to an activation energy of 0.6 eV T(L) = Temperature or life (usage) environment T(T) = Temperature of test environment C = 4.4*10^-4, with RH expressed in percent RH(T) = Relative Humidity (in percent) for test environment RH(L) = Relative Humidity (in percent) for life (usage) environment (NOTE: I think I did the parenthesis correct but I suggest you look at a copy of Klein Wassink or call me and I'll fax you this page.) Caveats: 1. This assumes that the effects of temperature and humidity are independent effects (not true in many cases/environments) 2. Assumes that you don't use a test environment that introduces new failure mechanisms (e.g. testing in condensing humidity when you don't see condensing in life environment or testing at temperature beyond Tg of PWB when such temperatures are seen in life environment. 3. Doesn't account for affects associated with electromigration (ie. voltage driven effects) Overall, our corrosion people think of this as a ROM for comparing environments but it is a case where there seem to be more exceptions to the rule than cases that follow it. Jim Maguire Principal Engineer, E/E M&P Boeing Defense & Space Group (206)657-9063 [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: Time Reduction of SIR Testing Author: [log in to unmask] at esdigate Date: 8/21/95 12:10 PM Address, Here at Hitachi Computer Products Division (Norman, OK) we introduce bareboards to extreme environmental tests. These tests are representative of 10 years of fault free life. However, these tests are extremely long and cut into our overall product life cycle. Without sacrificing bareboard quality, I am needing a time to temperature ratio for Humidity testing. i.e.. Our Humidity tests parameters are: a. >=800hrs b. 80?C (176?F) c. 90%RH d. R>10E9ohms @ 250VDC e. test times are every 50 hrs until 250, then at 500 and 800 purpose: we are evaluating the absorption and diffusion of moisture and moisture vapor. We are also checking metal migration, metal through migration and metal surface migration (SIR). Can anyone provide a time:temperature ratio for SIR testing? i.e.. for every degree increased or humidity, time can be increased or decreased by such. Please call and e:mail asap. Thank you. Thomas John Gulley (PCB Project Engineer) e:mail [log in to unmask] or 405-360-5500 x634 For several years I have been testing our customer bareboards