The best method of reporting defects is to calculate the ratio of "errors per possible errors", hopefully expressed in parts per million (ppm). So when you are placing parts, it is "placement errors per total number of placements". Or if you are printing solder paste it can be the "number of print errors per number of apertures". When you start using "number of boards with any error per total number of boards" it becomes impossible to compare results. Very simple boards with a low defect ratio does not mean you are performing well, and neither does a higher defect ratio for very complex board indicate that you are out of control. The "First Pass Yield" number that some people use (number of correct boards per total number of boards) has the same problem: you cannot compare a line that makes very simple boards to a line that makes very complex boards. But if you use ppm for all your work, any board can be compared to any other board and the data can even be combined for a complete plant. Have fun, Ahne Oosterhof A-Laser, Inc (503)641-9428 PS: But I have no idea how you do this for a circuit design engineer or even for a board layout person. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Roesler Sent: Monday, August 23, 1999 18:50 PM To: [log in to unmask] Subject: [TN] Defect Count Technetter's, When reporting defects, do I count all defects individually or do I count the number of bad circuits. For example, if I have a circuit which contains 3 defects, do I count this as 3 (for the 3 defects) or 1 (for the single, bad circuit). Thanks in advance for the clarification. Dave Roesler TRI-C Design, Inc. ############################################################## 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. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ############################################################## ############################################################## 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. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################