Jerry, It just doesn't make sense (to me anyway) to go to the effort of plasma etching to get adhesion, and they to use a silicone material. Silicones generally do not have good adhesion. I feel sure that if you use an acrylic or urethane material (providing your board is pretty clean) you won't have to plasma etch. Your comment about rework surprises me, I may be missing something? It has always been my experience that acrylics are a lot easier to re-work than silicones/RTV's. Do you want to chemically remove/rework or are you soldering straight through the product? I also agree with Brian about the danger of relying upon reported dielectric properties of a material measured at STP rather than at higher humidity if these conditions will exist in your end application. Alan Brewin Concoat Ltd. -----Original Message----- From: Brian Ellis <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Date: 26 May 2000 08:03 Subject: Re: [TN] Solder Mask >I'm sorry, Jerry, any coating that easily permits the passage of >moisture cannot have, by definition, good dielectric properties. The >dielectric constant will increase dramatically, as will the loss factor, >if there is moisture absorbed into the coating. Many RTVs even depend on >their moisture absorption to polymerise! If you want the best dielectric >qualities, some of the acrylics are unbeatable. > >Brian > >Jerry Mosur wrote: >> >> Actually we use RTV for its good dielectric properties, and not for its >> moisture blocking capabiliteis. >> The root of this problem lies in insuficient space for a given electrical >> characteristics of a circuit. If one can not open up spacing, one must >> resort to other techniques like routing the board in-between pads and >> encapsulating. >> As far as the conventional coatings go, we have found that in order to >> prevent delamination we have to plasma etch boards as well. With rework >> being easier with RTVs, we decided to use them instead. >> >> Graham, I will e-mail you for more info on solventless or water based >> coatins. How easy is the rework? >> >> Jerry Mosur >> >> Spellman High Voltage >> >> ############################################################## >> TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for additional >> information. >> If you need assistance - contact Keach Sasamori at [log in to unmask] or >> 847-509-9700 ext.5315 >> ############################################################## > >-- >Brian Ellis >Protonique SA >PO Box 78 >CH-1032 Romanel-sur-Lausanne, Switzerland >Voice: +41 21-648 23 34 Fax: +41 21-648 24 11 >E-mail: [log in to unmask] >URL: Technical and consultancy divisions: > http://www.protonique.com > Web services division: > http://www.protonique.com/webserv > >############################################################## >TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for additional >information. >If you need assistance - 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 1.8c ############################################################## 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 web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################