Try tin immerse or even a thin coating of oxide on one panel. If you suspect surface contaminates, this is a simple easy test that can be stripped off. If your problem is tape residue, good luck. That's a hard one to get rid of. (Until you remove the tape variable) Groovy ______________________________ Reply Separator _________________________________ Subject: Exposed copper after electroless nickel gold Author: [log in to unmask] at SMTPLINK-HADCO Date: 4/25/96 9:22 AM Recently we encounter exposed copper problem after electroless nickel gold process , we wish to know if there any way to determine the stubborn film on top of the copper that prevent the plating to take place . We understand that soldermask on pad or poor rinsing after final development could give rise to such problem . Such problem of soldermask on pad could be easily found after HAL but cases of minor soldermask on pad could not be detected in HAL . Please advise .