Hi Folks, I am interested in this exchange and I would like to drop my two cents. I am not an expert on this but I am under the following impressions: - Not ALL RTVs are equal, - ALL conformal Coatings absorb moisture at some rate, - There are PROs and CONs for all conformal coatings (ie. Rework, TC, resistance to Solvents - acrlyics poor, RTV good), therefore each application is different. I am interested to know what the moisture absorption rate for Acrylic is? Regards, Brent >>>>>>>>>>>>>>>>>> Original Message <<<<<<<<<<<<<<<<<< On 5/26/2000, 3:58:26 AM, Brian Ellis <[log in to unmask]> wrote regarding 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 ##############################################################