Craig, I agree, a bias is not required to get migration of corrosion products and a MFG test without bias will give you some relevant information, for example the presence of pores in a conformal coating. However, it will not cause electrochemical migration which is one of the more important failure mechanisms that you will have in harsh field conditions. Electrochemical migration often causes formation of dendrites and is an electrochemical processs requiring a bias to occur. It may occur beneath a conformal coating if contaminants (usually flux residues) are present in the interface between the coating and the board. If you have pores in the coating, i.e. poor coverage of biased surfaces, the dendrites may grow on the surface of the coating. Per-Erik Tegehall IVF, Sweden -----Ursprungligt meddelande----- Från: Craig Hillman [mailto:[log in to unmask]] Skickat: den 17 maj 2001 22:50 Till: [log in to unmask] Ämne: Re: [TN] ISA-S71.04 G3 "Environmental Conditions for Process Meas urements" The requirement of bias is not necessarily true. CALCE has conducted MFG tests, most recently on palladium-plated components, in which we have seen migration of corrosion products without bias. These migration products eventually travel to adjacent leads and lead to an increase in current leakage. Best Regards Craig -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Tegehall Per-Erik Sent: Wednesday, May 16, 2001 7:04 AM To: [log in to unmask] Subject: Re: [TN] ISA-S71.04 G3 "Environmental Conditions for Process Meas urements" 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 --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------