Earl, Rogers website has a lot of info on materials for RF applications... Some of the things we learned about RF were not necessarily intuitive. We made transitions from Wave guide to PCB and from RF connectors, SMA's, N-type, SMB's etc... Platings and process variations were problems. We typically used aluminum housings for RF products. Many screw locations to help with grounding, each discrete circuit was located in a shielded environment with a small pass thru to allow the RF signal to go on to the next circuit... originally we mounted all our PTFE boards on aluminum carrier plates and screwed them to the base. We found that the "one board" approach was the most cost effective and created a cover from machined aluminum to create the isolation needed. Thermal grease is still used in the industry, but nobody likes it. The silicone 'migrates' all over the inside of the assembly and can dry out in time and become non-functional. I suggest using the 'Sil-Pad' approach for thermal transfer where you can... but I doubt you will be able to avoid the silicone grease entirely. I saw some cool products for special thermal applications, a sort of foam loaded with ceramic particles was interesting, its thermal conductivity was much higher that I expected and it conformed to non-flat surfaces well. I have seen EMI reducing SIL-PADS used with a foil sandwiched between layers of silicon rubber that had a soldering tab that could be connected to ground for instance. Thermal expansion needs to be accounted for in RF assemblies, I have seen connecters break their connection to the board or lift the pad just due to the CTE differences in materials. Bill Brooks PCB Design Engineer , C.I.D. DATRON WORLD COMMUNICATIONS, INC 3030 Enterprise Court Vista, CA 92083 Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 mailto:[log in to unmask] IPC Designers Council, San Diego Chapter http://www.ipc.org/SanDiego/ http://home.fda.net/bbrooks/pca/pca.htm -----Original Message----- From: Earl Moon [mailto:[log in to unmask]] Sent: Wednesday, December 19, 2001 9:12 AM To: [log in to unmask]; Bill Brooks Subject: Re: Assembly of RF boards Sure like what you, and others, say about gold, OSP's, and silver. Wish you could convince 90% of the other engineers designing as if some very old "traditions" had merit. Also, thermal is a concern. Some of the amps get very hot. Some engineers really fight using any type thermal transfer improvement as grease or whatever. Earl Moon --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------