Andy, while potting is popular for structural strength, one also needs to be careful about both the curing process and the linear expansion tempco of the cured material. A power supply brick mfg. who shall remain nameless managed to mix a little too much catalyst and ended up with infant failures when the shrinking epoxy overstressed SMT resistors and capacitors. Regards, Steve At 08:35 AM 10/5/2004 -0400, Andrew Ingraham wrote: >You also would want to choose a potting material that doesn't exhibit >undesirable characteristics (i.e., loss) at the frequencies of interest. > >I know zilch (nothing) about the electrical characteristics of potting >materials, so I don't know whether there are lossy compounds that you need >to avoid. Certainly anything that is even slightly conductive, or sprinkled >with fine metal particles, would be bad. This sounds like something where >the electrical engineer should help specify the potting material and make >sure someone can't change the formula later, not realizing the electrical >impact it could have. > >I have seen L-C circuits that were potted. Because it's in such close >proximity to the coil's windings, it probably affects their self-capacitance >as well, so final tuning should take that into account. > >Regards, >Andy > > > Be sure to evaluate what the coating will do to the impedance of your > > PCB traces. If you intend to coat the board, design to account for that > > effect. Adding conformal coating to a properly operating board _may_ > > cause improper operation of the circuitry if you are depending on a > > particular impedance. > > > >------------------------------------------------------------------ >To unsubscribe from si-list: >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > >or to administer your membership from a web page, go to: >//www.freelists.org/webpage/si-list > >For help: >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > >List FAQ wiki page is located at: > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > >List technical documents are available at: > http://www.si-list.org > >List archives are viewable at: > //www.freelists.org/archives/si-list >or at our remote archives: > http://groups.yahoo.com/group/si-list/messages >Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu