Immersion gold deposits by their nature are porous. If the deposit looks uniform after plating, but after going through several rinses becomes discolored it would be wise to check the purity of the rinses. Perhaps something is being absorbed during subsequent processing. If the deposit looks discolored after plating, indeed the possibility exists of the gold bath being at its upper limit for nickel or copper concentration and these metals are codepositing. If these levels get high enough it will have an adverse effect on solderability and/or wire bonding. Another thing to check is if the deposit is of uniform thickness across all pads. If the discoloration occurs on thinner gold deposits after the plated boards have been in storage: this could be due to migration of Ni or Cu from beneath the gold surface. This too affects solderability and wirebonding (solderability less if using active fluxes. doug smith <[log in to unmask]> on 02/17/99 03:17:48 PM Please respond to "\"TechNet E-Mail Forum.\" <[log in to unmask]>, doug smith" <[log in to unmask]> To: [log in to unmask] cc: (bcc: Bruce Stacy/ECSDOMAIN) Subject: [TN] Immersion Gold contaminated with Copper I am observing a variation in the color of gold immersion finished boards. My theory is the gold finish is being contaminated by subsequent cleaning processes prior to assembly. Does anyone have any experience with copper contamination of immersion gold? I know that nickel is used as a barrier between the copper SMT pad and the gold finish. Without the Nickel barrier the copper would migrate into the gold creating an unsolderable finish. So there is a chemical reaction possible between copper and gold. So what if the gold immersion finish is subjected to subsequent processes in the fabrication facility that have copper in solution. Is the copper attracted to the gold surface out of solution? Can the concentration of copper in solution be so high as to make the gold finish unsolderable? Is there an acceptable limit of copper contamination in an immersion gold finish from an assemblers solderability viewpoint? Doug Smith Technical Support Engineer Yamamoto Mfg. (USA), Inc. (408)944-8308 [log in to unmask] ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################