John, I have set up 2 such solder paste measurement systems. One at my previous employer and now one at my new employer. In both cases I choose the Alpha Hi-check system over the Cyberoptics unit. But, regardless of the equipment you should try to measure to the pad surface. If you are undercutting you stencils at all (most do) you will have some exposed pad to measure to. This will give you your truest number as far as the actual thickness goes. In experiments where I did not have any stencil reduction I would measure pad height from substrate, then print, then measure substrate to paste and find the difference. But in production we use the edge of the pad from the stencil reduction to the paste. We measure 5 locations on a board: all 4 corners and the center- however if BGA or fine pitch is used those are measured. We measure the 3rd piece of each run (not the first of second because of paste kneading), and the again at the mid point of the run. If you are using organic coating instead of HASL and are not worried about the true paste thickness you could measure from the substrate to the paste. The copper should be consistent enough to give you the consistency you need. This will allow you to track the consistency of the paste printing process, just not necessarily the true paste thickness. My recommendation is to use the actual pad surface if at all possible. Good luck, Brad Kendall ############################################################## TechNet Mail List 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://www.ipc.org/html/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################