One thing to look at would be the possibility of copper being complexed with the amines from the resist stripping solution. While each metal has a specific deposition potential as an uncomplexed entity, these potentials can be altered if that metal becomes chelated with amines, EDTA, etc. > -----Original Message----- > From: Lourdes Mertens [SMTP:[log in to unmask]] > Sent: Thursday, February 18, 1999 7:56 AM > To: [log in to unmask] > Subject: Re: [TN] Immersion Gold contaminated with Copper > > How would you explain copper stains on electrolytic gold ( hard or soft) > after it's been immersed in an amine based resist stripper at 140 F for > about 15 minutes. The panels are copper, solder plated and selectively > gold plated before resist strip. > > Lourdes Mertens > >>> "<Rudy Sedlak>" <[log in to unmask]> 02/17 8:51 PM >>> > In a message dated 2/17/99 4:14:33 PM Pacific Standard Time, > [log in to unmask] writes: > > << > enough time) When I dropped a nickel/Iron component into the bath it > immediately plated with the copper. > > Perhaps one of the > plating gurus can explain the likelihood of electroless copper plating > onto > gold. >> > > You are confusing electroless and immersion plating. > > When you plate electroless, something in the bath, called a reducing agent > causes the metal to plate out, this can be Formaldehyde, or Sodium > Hypophophite, or many others. > > When you immersion plate, the substrate dissolves, and this causes the > metal > in solution to plate. One of the classic examples is putting a nail > (iron) > into an acidic Copper salt (like Copper Sulfate) solution. This is what > happened when you did your experiment. The fact that there was Nickle in > the > Iron was incidental to what happened. > > It is difficult to explain clearly, but there are rules about what metal > can > immersion plate on to another, and roughly speaking, in order for a metal > to > immersion plate on to another metal, the metal in solution must be more > "noble", or less readily oxidized, than the substrate. This is why Gold > can > immersion plate on to Copper, but Copper cannot immersion plate on to > Gold.... > > I'm tired, I am gonna stop now... > > Rudy Sedlak > RD Chemical Company > > ################################################################ > 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 > ################################################################ ################################################################ 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 ################################################################