Dave - Tenting of vias is a wise precaution to reduce the potential for intermetallic growth formations between exposed conductors. The more exposed metal you have under part bodies and in hard to clean areas, then the greater the risk that some small amount of process residue, coupled with moisture and operating current, will become a problem. Vias themselves can also represent a cleaning problem, simply from their small size. Even though solder mask is not to be used as a conformal coating, you will note that its dielectric values and process durability are quite respectable for this purpose. A word of caution: some of the less durable solder masks are not necessarry acceptable to tent vias. The heat of soldering can generate considerable pressure from the atmosphere in a via, causing the mask tent to rupture. Recommend you test this thoroughly, as ruptured via tents tend to inhale process fluids as they cool following soldering. As with any solder mask application, IPC-SM-840 indicates that the user must confirm compatibility with his own processes and applications. We have encountered a number of masks which are susceptible to some of the non-CFC cleaners, as well as a few which reacted to various fluxes. Regards - Kelly ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################