Hello Technetters: Recently we are having a problem on our black oxide layer color. After pressing (especially for 4 or 6 layer board with thin outer prepreg, e.g. 2116 single ply), the black oxide around the edge of some boards seemed to turned red. This caused particularly low yield recently. Can anyone knidly give some advice, or have some experience on such issue? Darik Leung Mica-AVA (F.E.) Ind. Ltd. / Oriental Printed Circuits Ltd. (HK) Quality Assurance [log in to unmask] What do you see after oxide processing before layup? typically it is caused by two things: Either a temperature issue during the run thru or a concentration drop in the oxide chemistry. I have seen two other instances one is copper/laminate supplier using too much chromate conversion coating and the other was very thick cores. *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************