I can successfully protect a 30 Mohm impedance circuit from standing water (at 120 V) using a sprayed silicone coating for a couple of minutes using one of several coatings. Silicones work the best. ______________________________ Reply Separator _________________________________ Subject: Re: conformal coating help Author: [log in to unmask] at internet Date: 1/22/97 8:00 AM << We need to provide 100% moisture seal on the top surface of some FR-4 boards about 8"x12" that have SMT components mounted. Can I do this "easily" in-house without much equipment? What materials and suppliers? We could easily install a fume hood if necessary. This is not a high volume project. What do I do about sealing vias? thanks, Crawford Byxbee >> Crawford, There is no such thing as a 100% moisture seal with conformal coatings. All of them are organic polymers, which have varying levels of moisture permeability. Water WILL get through, it is only a matter of when. Better to ask the question of why you feel you need to have a 100% moisture seal. Of the available coatings, you should probably try a silicone (type SR) coating or parylene coating. Since your volume is low, sending the product off for parylene coating, avoiding capital investment, may be your best bet. You might also consider a contract conformal coater. Doug Pauls CSL [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************