You have a bad pre-cleaning line. Your soft-etching or micro-etching does'nt thoroughly remove some oxides on your copper. Thick oxides are difficult to remove esp those boards after soldermask cure. Try to check your copper surface condition. Etching rate during acid etching. Apperance of gold and Ni only adopts the condition of the underlying metal such as copper. hope this helps "Scott B. Westheimer" <[log in to unmask]>@IPC.ORG> on 09/21/2000 08:41:50 AM Please respond to "\"TechNet E-Mail Forum.\" <[log in to unmask]>, \"Scott B. Westheimer\"" <[log in to unmask]> Sent by: TechNet <[log in to unmask]> To: [log in to unmask] cc: Subject: [TN] ENIG I was wondering if those of with experience running ENIG line could help me with some issues we are encountering. What is the reasons for discoloration of gold? We have tried rinsing in hot DI, drying immediately after coming out of the gold solution as to not allow water to dry on the surface, but we still encounter small amounts of tarnish or discoloration. This is new for us and your help would be appreciated. Scott B. Westheimer ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8d ############################################################## 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://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################