Ed, Are you using a handheld device (eddy current?) or a benchtop unit (x-ray fluorescence). I have very limited experience with a handheld unit, but we used to have a CMI x-ray fluorescence benchtop unit for measuring metal thicknesses. Most of our errors used to be due to what (copper, no copper) was in the layers underneath the area that we were measuring. We had to be fairly specific where a measurement was taking place. We also would see errors due to metal density fluctuations. Are you sure that the copper isn't smearing during the cross-sectioning process? Is it nickel gold plated? Do you etch the copper after polishing? The differences that you are seeing seem to be large for smearing, but I thought I would ask. As an aside, one of the responses mentioned room-temperature annealing of copper. At a past employer, this was mentioned quite a few times as well. Does copper really anneal at room temperature? I was always taught that annealing was an elevated temperature operation (deformed, stressed grains are consumed and regrown). As a rule of thumb, recrystallization occurs at 0.3 to 0.5 times the melting point of the material (on the order of 325 - 525 C for copper). There was a process called "Recovery" in my textbooks which occurs from room temperature to ~300 C for copper. It involves the annihilation of dislocations, reducing the internal stresses. Is this what's causing the shift in electrical properties? I didn't mean to veer from the original question, but this room temperature annealing thing has been bothering me for some time. Can anyone explain the phenomenon? I haven't been much help to Ed, but maybe I can learn something. Dave Anderson Medtronic, Inc. Reply separator------------------------------------------------------------------ Hi all, Just a question. I have been having problems getting my CMI unit to read = copper thickness consistently. It has typically been reading low. For = instance, the meter will show .0005 to .0006 of copper on a standard = .042 thru hole but a section of the same hole shows .0012. The meter = reads fine to the provided standard. Has anyone else experienced this = problem. I should note that the meter was just calibrated a few weeks = ago so calibration should not be an issue. Ed Cosper ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ 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://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ 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://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################