Following from the EMPF HelpLine, prepared by Jeff Kukelhan: There are two types of gold coatings available: electrolytic and electroless. Electrolytic is usually thicker (50 to 100 microinches). It is often used for mechanical contacts (edge connectors), although I have seen electrolytic gold used for solderable surfaces. The more common finish for solderable surface mount boards is immersion (or electroless) gold. The copper pads are first plated with about 50 microinches of Ni. When immersed in the Au bath, some of the Ni enters solution and reduces the Au. The Au precipitates out on the Ni surface. The process is self limiting because eventually all of the Ni is covered with Au. When there is no Ni left to go into solution, no more Au will percipitate. The resulting Au coating is about 5 to 15 microinches thick. The amount of Au covering the pads is so small that when covered with a nominal amount of solder paste it will not embrittle the resulting joint. I have copies of two articles printed within the last two years that deal with immersion Au coated boards, and how to avoid joint embrittlement. If you are interested in obtaining copies, contact the EMPF HelpLine at 317.226.5616 or [log in to unmask] (alt short address [log in to unmask]) ---------- From: TechNet-request To: TechNet Subject: Gold Flash Coating Date: 4 Dec 95 2:29PM Return-Path: <[log in to unmask]> Resent-Date: Mon, 4 Dec 1995 15:37:54 -0500 Old-Return-Path: <miso!grci.com!lbrown> Date: Mon, 4 Dec 95 14:29:57 PST From: Len Brown <[log in to unmask]> Sender: Len Brown <[log in to unmask]> Subject: Gold Flash Coating To: [log in to unmask] X-Mailer: Chameleon - TCP/IP for Windows by NetManage, Inc. Message-Id: <[log in to unmask]> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Resent-Message-ID: <"ZYfRw1.0.w2D._tqmm"@ipc> Resent-From: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/1970 X-Loop: [log in to unmask] Precedence: list Resent-Sender: [log in to unmask] ---------------------------------------------------------------------------- -- I am looking for information conserning gold flash on pc boards. Pros & cons of gold. 1) Does it create a better surface for fine pitch surface mount parts? 2) Is there any possibility of embrittlement of solder joints? Any information will be appreciated Thanks in advance. ************************************************************************* * * * Len Brown GRC International, Inc. * * [log in to unmask] 8310 Guilford Road, Suite A * * 410-290-7111 x240 Columbia, MD 21046 * * fax 410-290-7122 * * Date: 12/04/95 Time: 14:29:57 * *************************************************************************