Paul, I think what you are looking for here is a calculation of DPMO, or Defects Per Million Opportunities. These calculations of defect rates are normalized by the complexity of the board using a calculation for the number of opportunities per boards, based on the number of components and the number of pins. You can find information on this in IPC-7912, Calculation of DPMO and Manufacturing Indices for Printed Board Assemblies. You can also find some related, but more general information in IPC-9191, General Guidelines for Implementation of Statistical Process Control (SPC). If you search the publications list on www.ipc.org, you may find other related publications on DPMO. On a related note, we use a software package from Tecnomatix-Unicam that calculates the DPMO values, overall and for individual defects, based on the defects that are logged against each board and the opportunity count, which is calculated from the Unicam job file used to set up each board type. Let me know if you would like additional information on this. Dave Roach Trane GCC 4833 White Bear Parkway St. Paul, Minnesota 55110 651-407-4294 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Baine Sent: Friday, August 12, 2005 10:30 AM To: [log in to unmask] Subject: [TN] Calculation of solder defect rates Hello all, I have not used this forum for a few years so I hope I'm doing this right. I have a question re calculation of defect percentages for PCB Assemblies. The old MIL-STD-2000 standard defined a "defect rate" as the number of observed defects divided by the "normalizing number". The standard requires calculation of the following: (1) an Assembly Defect Rate, which is the assembly defects divided by the normalizing number, where Normalizing Number is (total no. of components, component leads, terminals and wires on the assembly plus one for the PWB); and (2) a Solder Defect Rate, which is the solder defects divided by the normalizing number, where Normalizing Number is (total no. of terminals plus total no. of solder connections). I cannot find any guideline in J-STD-001 or IPC-A-610 for calculating defect rates. I am trying to find some non-time- consuming method for calculating the Normalizing Numbers. For example, would the Solder Normalizing Number just be the total no. of component leads? I would appreciate some guidance. Thanks in advance. Paul Baine Q.A. Manager C-Tech Ltd. Cornwall, Ontario, Canada --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------