Hi Brian, This assumes that the type of contamination, and thus the speed of dissolving, is always the same. From experience I know that the speed at which the asymptote is approached varies a lot from product to product, depending on design, bare board materials, components. But maybe that's one of the reasons why you already called it a very rough guideline. For practical reasons we've set the standard measuring time for our Alpha Ionograph to 15 minutes. Kind regards, Daan Terstegge Unclassified mail Personal Website: http://www.smtinfo.net >>> Brian Ellis <[log in to unmask]> 10/23 2:55 pm >>> Albert How long is a piece of string? It depends on how quickly the contaminants dissolve. I suggest you do two or three tests for an hour. You will observe that the resistivity drops fairly rapidly and then very slowly. Draw a straight line approximating the last 15 minutes backwards to zero time. Draw another straight line approximating, say, the first five minutes. Note the value and the time where the two lines intersect. If the value is > 3/4 of the final value, then double the time to intersection. If >1/2, then quadruple the time. If >1/4 then octuple the time, if <1/4 then 16 times the time. This is only a **very** rough guideline until you acquire sufficient experience to judge when you approach asymptote. Brian > ¿àÁJ·½( sylai ) Q80_5381 wrote: > > Hi TechNetters, > I need some help regarding Cleanliness. Now I have an automatical > test machine whose name is omega 600. I usually test 10 minutes > for cleanliness of PCB. Can anyone give me the best advice about the > test time of omega 600 machine which is used in PCB and tell me the > cause ? > Thanks, > > Best Regards, > > >Albert Lai > > TEL : 886-3-323-1111 ext 5381 > > FAX : 886-3-323-6611 > > E-MAIL : [log in to unmask] --------------------------------------------------------------------------------- TechNet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF TECHNET Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 --------------------------------------------------------------------------------- --------------------------------------------------------------------------------- TechNet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF TECHNET Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------