To be more specific, the tests were originally designed to accelerate corrosive degradation processes on contact surfaces. They were developed in a hugh research programme led by the Battelle Institute in the eighties. For corrosion of contact surfaces the test methods were proved to be relavent and the acceleration factors are only valid for that case. For other types of corrosion mechanisms, the relevance of the test has not been evaluated to my knowledge. Since contact surfaces are not conformally coated, conformally coated samples were included in the original work. Electrochemical migration, which is on of the major failure mechanisms that you want to prevent by conformally coating, would not be cover by the MFG tests unless a bias is applied to the assemblies during the test. Per-Erik Tegehall IVF SWEDEN Phone: +46-31-706 6148 Fax: +46-31-27 61 30 Email: [log in to unmask] Homepage: http://www.ivf.se -----Ursprungligt meddelande----- Från: Barmuta, Mike [mailto:[log in to unmask]] Skickat: den 15 maj 2001 22:38 Till: [log in to unmask] Ämne: Re: [TN] ISA-S71.04 G3 "Environmental Conditions for Process Meas urements" Paul: This type of testing is commonly caled Mixed Flowing Gas or MFG. This test simulates environmental exposure through controlled temperature, humidity and the introduction of trace quantities of corrosive gases in an enclosed chamber. It is designed to accelerate corrosive degradation processes. Measured hours of chamber time can be correlated to years of exposure in the field. There are increasing degrees of severity for different environmental exposures ie business office, light industrial, refinery, water treatment plant etc. These are called out as method G,H and K, with increasing corrosive effects. Gases used are H2S, SO2 and chlorine in ppb ranges. These then contribute to varying degrees of oxidation and corrosion of the PCB. We have used the Microelectronics Div of IBM, Endicott N.Y.(800-934-0104)for our testing. This was a few years back, not sure if they are still around. There are other that can do the same testing. Regards Michael Barmuta Staff Engineer Fluke Corp. Everett WA 425-446-6076 -----Original Message----- From: Paul Bannister [mailto:[log in to unmask]] Sent: Tuesday, May 15, 2001 11:36 AM To: [log in to unmask] Subject: [TN] ISA-S71.04 G3 "Environmental Conditions for Process Measurements" Does anyone have information about the effects of corrosive gases on printed circuit board assemblies. Specifically what I am interested in is what happens to PCB's when exposed to corrosive levels as described in ISA-S71.04 G3 (Harsh) specification, what is the failure mode? We are conformally coating our printed circuit boards now to meet this specification but it is not clear to me what would happen to the PCB if it were not coated. Do people meet this specification without conformal coating? --------------------------------------------------------------------------------- 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 To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives 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 ---------------------------------------------------------------------------------