Mail*Link(r) SMTP FWD>RE>Silver Plating over Copper To all: I agree with all the things Dave mentioned and would like to add the following: Silver (Ag) plating is frequently used in sensitive rf (radio frequency) and other high frequency/speed applications. Ag is used for two main purposes; first due to "skin effect", silver is one of the better conductors, and because most electrical current flow is in the outer surfaces of conductors (where the greatest electrical field intensity and currents are) and Ag is one of the best. The other reason is because most Ag compounds and oxides are electrically conductive, in contrast to Cu's which are generally poor electrical conductors. With the exception of gold, most other surface platings and coating (solder, etc) are lousy conductors and are seldom used for serious high frequency/speed applications. If the design is for microstrip lines, then the Ag plating will be less effective at very high frequencies >~1 GHz because most of the electrical current flow is between the surface of the microstrip that is adjacent to the signal reference (ground) plane and not on the "outer" surface of the microstrip. Ralph Hersey [log in to unmask] -------------------------------------- Date: 7/3/96 6:55 AM From: ddhillma Hi Ed: Silver plating over copper - that can be a solderability issue if not done correctly. The copper will diffuse through the silver after a period of time and then oxidize making for a solderability nightmare. We have gotten around this issue by making the silver plate very thick - this takes care of the diffusion issue but makes for a more expensive board. Silver plating also likes to tarnish quickly and can be a handling problem on the manufacturing floor. Is there a functional need for a silver plate? Could gold or tin/lead be substituted? A good article on finishes (plus very good references) to look at is "Connector Reliability in The Military Environment", Connection Technology, May 1989, pages 19-22. Dave Hillman Rockwell Collins [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: Silver Plating over Copper Author: [log in to unmask] at ccmgw1 Date: 7/3/96 7:44 AM This is mostly addressed to PCB fabricators, but anyone else with relevant info please e-mail back to me. One of our new customers has a requirement for SILVER PLATING OVER COPPER and then covered with solder mask similiar to SMOBC (SMOBC/S ?). Do any of the shops out there in the technet world do this? Secondly, my customer is looking for the best laminate with low Df and low Da. Is teflon the best or would somone recommend another laminate to use? The laminate would the use the above silver-plated copper. Please contact me in any of the following methods: (1) via [log in to unmask], (2) [log in to unmask], (3) Ed Valentine at ProTronics, Inc. Telephone: (919) 217-0007 or Fax: (919) 217-0050. Thanks . . . Ed/ ------------------ RFC822 Header Follows ------------------ Received: by quickmail.llnl.gov with SMTP;3 Jul 1996 06:55:22 -0700 Received: from ipc.org by simon.ipc.org via SMTP (940816.SGI.8.6.9/940406.SGI) id IAA24108; Wed, 3 Jul 1996 08:46:55 -0700 Resent-Date: Wed, 3 Jul 1996 08:46:55 -0700 Received: by ipc.org (Smail3.1.28.1 #2) id m0ubRon-0000EZC; Wed, 3 Jul 96 08:18 CDT Resent-Sender: [log in to unmask] Old-Return-Path: <[log in to unmask]> Date: Wed, 03 Jul 96 08:19:37 cst From: "ddhillma" <[log in to unmask]> Encoding: 43 Text Message-Id: <[log in to unmask]> To: [log in to unmask] Cc: [log in to unmask] Subject: Re: Silver Plating over Copper Resent-Message-ID: <"RuLR23.0.c38.7Cdsn"@ipc> Resent-From: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/4966 X-Loop: [log in to unmask] Precedence: list Resent-Sender: [log in to unmask]