Concerning I.R. reflowed plated Tin/Lead on single and double sided PCB's. What can cause poor adhesion of the reflowed Tin/Lead to the plated copper pad? Our plating process is : acid copper/h2o rinse /fluorboric dip/fluorboric Tin/lead plating/ etch/ I.R. reflow. The "problem" is only seen on one or two panels in a particular lot, and comes and goes, sometimes with months in between occurances! Sometimes its detected by a random tape test at pre-mask inspection...sometimes, "unfortunatly" it's found after the customer has assembled the PCB. The solder joints appear to flow very well, but will seperate from the copper if pressure is applied the component lead. No copper is attached to the solder joint that has lifted. The copper pad below is usually somewhat oxidized. We have explored many possible causes, including excessive hold time between steps, etc. I would appreciate any thoughts on this, if anyone has some ideas...?