Here is a very interesting web site put out by a vendor, but it addresses an awful lot of the issues we are discussing. http://www.enthone.com/ Gary -----Original Message----- From: Robert Wilson [mailto:robert_wil...@tirsys.com] Sent: Monday, June 03, 2002 9:01 AM To: Jim Conrad; Chris Wells; EMC-PSTC Discussion Group Subject: RE: Bonding to conductive plastic - best method??
The first of your suggestions will not work with the material Chris is using. Any polymer that has conductive material mixed in, tends to form a thin skin of pure resin at its surface. A conductive paint or epoxy applied to the surface will not come in contact with the metal strands, and all you will mainly get is capacitive coupling. Further, applying a silver-loaded epoxy to the surface of most metals (including stainless steel) will not penetrate that material's natural oxide layer and hence (unlike what most people I've talked to seem to think) will NOT produce a reliable electrical connection, even when applied directly to the metal. A reliable electrical connection to any metal requires that one must cut through the metal's oxide layer. Thus, your second suggestion is more workable, although he is basically using these already (the plastic screws he refers to are very similar to sheet metal screws). Bob Wilson TIR Systems Ltd. Vancouver. -----Original Message----- From: Jim Conrad [mailto:jc...@shore.net] Sent: June 2, 2002 4:34 AM To: Chris Wells; EMC-PSTC Discussion Group Subject: RE: Bonding to conductive plastic - best method?? Hi Chris, I would try a Silver loaded conductive epoxy or use SS self tapping screws. Jim -----Original Message----- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Chris Wells Sent: Friday, May 31, 2002 10:23 PM To: EMC-PSTC Discussion Group Subject: Bonding to conductive plastic - best method?? ----- Original Message ----- From: Chris Wells <mailto:cdwe...@adelphia.net> To: EMC-PSTC Discussion Group <mailto:emc-p...@majordomo.ieee.org> Cc: christopherdwe...@eaton.com Sent: Friday, May 31, 2002 8:07 AM Subject: Bonding to conductive plastic - best method?? Recently we had a good string going on conductive platics. I would appreciate some help coming up with the ideal electrical bond to this type of plastic. We use a 6% Stainless Steel Fiber mix in Poly carbonate and I was looking for the best method to electrically bond to the plastic to drain off ESD or for high frequency bonding with the metal portion of our product. This would include Printed Circuit Board to plastic, Cable to plastic and metal housing to plastic type connections. For joining metal housing and PCB connections we have been using plastic screws that mechanically are designed for plastic. The threads are widely spaced, tall and thin - They cut into the plastic with out breaking the mounting bosses (studs). The engagement with the plastic (screw thread in plastic boss hole) is ~ 100% leaving little or no air gap between the screw and the plastic. First set of Question - If using screws what would be the best type of screw to insure good contact to the stainless steel fibers? * High profile, thin thread, plastic screw like I described? * Self tapping type screw? What should the platting be? * Clear Zinc * Zinc Chromate? * Nickle on brass? * Stainless Steel? Is there any sort of liquid/paste like adative that could be added to the screw hole to enhance the electrical connection? We have experimented with metal inserts (PEM nut brand for example). What sort of bonding does one get when molded in? I suspect poor relative to press in. Can the inserts be plain brass or should they be plated like with nickle? Depth of inserts - Longer inserts should be better but I am concerned about cracking of the boss. Screen matterial in the screw boss. I have seen screen matterial embedded in conductive plastic. Perhaps it could help screws bond to the plastic as well. Any comments? Sounds messy. Coatings on top of conductive plastic? If a coating were placed on the inner surface of the conductive plastic it might make a good hybrid sollution but costly. Are there other considerations? If you respond today try CC to christopherdwe...@eaton.com So I get it at work too (the ITE guys can't handle this subscription list at work) This group is the best resource I have for this sort of topic - thanks in advance!! Chris Wells Senior Design Engineer Cutler-Hammer Pittsburgh, Pa. USA christopherdwe...@eaton.com
