Hello All! I lost the original post on this subject, so I will use Dougal Stewarts' post to reply. I haven't seen this one (purple stain) for quite awhile! In the "early days" of reflowed tin/lead, we put the nickel/gold onto edge card tabs right after etching but before reflow. The plated tin/lead was easy to strip off the fingers and the process went well. With the advent of HASL, it was a pain to nickel/gold plate prior to HASL because of the infamous finger taping issues prior to HASL. So we nickel/gold plated after HASL. HASL solder was quite difficult to completely remove without both chemicals AND abrasion in the inline tab plater. We began to get the purple stain which turned up at soldermask bake and got worse as the board saw more and more heat. Our labs tested the product and found that in some rare instances that there could be an ionic issue but not as disastrous as the cosmetic issue. We decided to eliminate the cosmetic issue entirely by finding a better way of taping the nickel/gold prior to HASL. The purple stain itself is caused by a complexing of the Cobalt in the gold with the Bromine in the laminate under heat. We suspected that somehow the aggressive HASL solder strip chemistry combined with abrasion provided a better path for the gold salts into the laminate. We don't make boards anymore, but occasionally we get a few supplier questions regarding acceptance. I hope this helps. Gerry -----Original Message----- From: Stewart, Dougal [SMTP:[log in to unmask]] Sent: Thursday, May 21, 1998 4:05 AM To: [log in to unmask] Subject: Re: [TN] DISCOLORATION Purple discoloration on gold plated boards is due to the formation of 'purple of Cassius', which yu should be able to find out about in your chemistry books. I believe that it is due to some contamination absorbed into the resin of the laminate. I remember this problem 15 years ago, and a change of laminate supplier had the problem go away. Dougal Dougal Stewart Product Development Manager Viasystems Selkirk Ltd Selkirk, Scotland, TD7 5EJ Tel: +44 1750 21601 Fax:+44 1750 22513 email [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 web site (http://jefry.ipc.org/forum.htm) for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################