Follow-up to your questions: Background Plating Pretreatment Factors While different supplier processes rely on a number of different process chemistries to achieve an active surface for the nickel bath to initiate plating, all processes share the following needs : Control of chemistry with appropriate concentration, bath operating condition and bath age limits Control of process rinsing quality and times Beyond these factors, the relative process windows for resistance to background plating of #different suppliers systems may very well be different. Nickel Plating Bath The following observations apply to nickel baths in general. The tendency towards background plating may be caused by operation of the bath at : Excessive levels of plating rate / activity Low levels of bath stabilizer These conditions correspond to either excessive bath additions or inadequate frequency or quantity of replenishment materials. As a first step, baths should be operated within the control limits established by the product supplier. Inadequate filtration might also lead to a build-up of fine particulate matter in the bath that could act as initiation sites for background plating. In addition, there will be differences between the performance of different suppliers products. The desired combination of good plating rate and resistance to plating initiation on areas other than activated copper is a function of the specific bath formulation chosen. Substrate The substrate can influence the process in several ways. Failure to completely remove all the copper from the areas between traces, even at a microscopic level may lead to plating on those particles. Treatment of a sample of the work being processed with oxide can help to make these fine copper particles more visible under inspection. If use of a longer microetch immersion time has a beneficial effect on background plating performance, this mechanism may be operational. The texture of the substrate epoxy may also be an influence. Higher profile foils will leave behind a more deeply textured epoxy surface. This may in turn lead to greater difficulty rinsing residual activation chemistry from these areas, leading to inadvertent activation of resin areas. Longer rinse times or use of tempered rinses may be of benefit in this case. Hope this helps. Regards, John S. Grosso Shipley *************************************************************************** * 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] * ***************************************************************************