Nope, no problems. There was an under plating, Copper I think, but don't quote me on that. We made large circulators, cavity filter, and diplexers by hogging out Aluminum blocks and then plated the silver finish all over the part. It worked like a champ. There was an onsite chemical engineer there who was very helpful in coming up with solutions to problems. They also were pretty self contained, making their own boards, gaskets, aluminum parts, plating, testing... it was an amazing place. http://www.remec.com/products/market_results.cfm?market_key=1&category_key=3 &type_key=7 The pcb's we did were either Hasl, gold, or unplated with OSP. Depending upon end use and processing. If you want to know more about their silver process I think you will have to contact REMEC's engineering dept. I worked there back in the 90's and couldn't tell you who exactly to contact. There is most likely someone there that can tell you about silver plating over aluminum issues if it's not deemed proprietary or something. Best regards, Bill Brooks - KG6VVP PCB Design Engineer, C.I.D.+, C.I.I. Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 Datron World Communications, Inc. _______________________________________ San Diego Chapter of the IPC Designers Council Communications Officer, Web Manager http://dcchapters.ipc.org/SanDiego/ http://pcbwizards.com -----Original Message----- From: Stadem, Richard [mailto:[log in to unmask]] Sent: Tuesday, May 17, 2005 11:23 AM To: TechNet E-Mail Forum; Brooks,Bill Subject: RE: [TN] Best plating for 10-15 GHz (Ku band?) We had thought about using that combination at one time, but the plater told us that it was difficult to do because of the AI difference between the two alloys, even plated. The anodic index for the silver is around .03, and aluminum, if I recall, was around 1.4 or something like that, so if the plating was not done perfectly the dissimilar metals literally eat away at each other and any other hardware (brackets, stainless steel screws, chromium-plated SBA connectors, etc.). Did you have any problems with that? -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Brooks,Bill Sent: Monday, May 16, 2005 10:35 AM To: [log in to unmask] Subject: [TN] Best plating for 10-15 GHz (Ku band?) You comments confirm my experiences as well. Working in the 2 to 6GHz range we used OSP to protect the board until soldering time, and afterward the bare copper was the only finish. This was on Rogers' 4003 material. Solder mask is also very lossy to RF so we reduced the amount of masking to a small strip of soldermask we called a 'solder dam' that prevented the wicking effect of the trace to pad interface during reflow but did not cover the whole board with soldermask. After assembly the board was cleaned and allowed to oxidize normally, which of course protects the copper after it oxidizes, and is a self healing natural protectant for copper. Why do you suppose they used it for roofing and piping in homes? The EE that was doing the simulation for the circuit remarked that the nickel under plating was very lossy to RF and that copper oxide on the surface would not affect the RF signal at all. The signals we were working with were very low power and would disappear all together if they were run down a nickel plated transmission path. We made a lot of high powered RF filters and they were constructed of Silver plated Aluminum. Silver is a better conductor than gold, contrary to some people's assumptions, and silver oxide is still very conductive, not like most metals that have insulative properties when they oxidize. The only downside to silver was it's sensitivity to being exposed to sulphur which made a silver sulfide when exposed which turns black and is very non-solderable... So we had to make sure there were no natural rubber compounds in the package that would outgas the sulphur compounds that remain in them during processing and ruin the silver plating. http://en.wikipedia.org/wiki/Silver_sulfide Interesting thread... Best regards, Bill Brooks - KG6VVP PCB Design Engineer, C.I.D.+, C.I.I. Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 _______________________________________ Member of the San Diego Chapter of the IPC Designers Council Communications Officer, Web Manager http://dcchapters.ipc.org/SanDiego/ http://pcbwizards.com -----Original Message----- From: Stadem, Richard [mailto:[log in to unmask]] Sent: Monday, May 16, 2005 7:33 AM To: [log in to unmask] Subject: [TN] FW: [TN] FW: Possible Lead -----Original Message----- From: Stadem, Richard Sent: Monday, May 16, 2005 8:18 AM To: [log in to unmask] Subject: RE: [TN] FW: Possible Lead The actual answer is silver, or rather, copper, which is what you are really soldering to with a silver finish. The reason for this is because at these extremely high frequency/high impedance ranges the signals tend to migrate to the surface due to the skin effect (Hall effect). The final finish itself has nothing to do with the conductance, as that is quickly absorbed into the solder joint itself. What affects the overall impedance is the conductivity of the basis metal. In an immersion silver finish, the silver is absorbed into the solder joint, and copper is the conduit. In an immersion gold finish, nickel is the underlying conductor. Copper's resistivity is 1.67 uohms per centimeter. Pure nickel's resistivity is 7.4 uohms per centimeter. However, due to the phosphorus that is added to the nickel surface as part of the plating process, its actual resistance can climb as high as 90 uohms per centimeter. It has been documented in various papers that the signal loss is around .0015 Db per inch for copper, and about .012 Db per inch for nickel. Note that nickel has nearly 10 times the signal loss. The circuit's accumulated resistance through all of the solder joints where nickel is the basis metal adds up to the net loss factor. Also, I believe the immersion silver finish is less costly than that of immersion gold over electroless nickel. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo Sent: Friday, May 13, 2005 4:11 PM To: [log in to unmask] Subject: Re: [TN] FW: Possible Lead silver! and costly one...jk -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of David Douthit Sent: Friday, May 13, 2005 3:39 PM To: [log in to unmask] Subject: Re: [TN] FW: Possible Lead Charlie, GOLD!! David A. Douthit Manager LoCan LLC Charlie McMahon wrote: >Question: > > > >What is the optimal surface finish for PCBs working in the frequency >band >10-15 GHz? > > > > > >Charlie McMahon > >McMahon Sales Company > >P.O. Box 1024 > >Windham, New Hampshire 03087 > >Tel: 603-432-3111 > >Fax: 603-432-6854 > >Cell: 603-401-4646 > >e-mail: [log in to unmask] > > --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------