PPM= defects found/possible defects X 1,000,000 Possible defects are all parts on the board, the board and all terminations. A misaligned component with off pad leads can be counted as a misaligned component or as some number of leads off pad , but not both. A missing soic8 can be a missing part or 8 open joints, but not both. In order to use the PPM as a tool and as a metric of "goodness" of an assembly, I prefer to assign the number of joints failing an acceptable inspection and then use an unacceptable PPM rate as a prompt to analyze the cause(s) of the unacceptable defect rate. > -----Original Message----- > From: [log in to unmask] [SMTP:[log in to unmask]] > Sent: Tuesday, April 28, 1998 5:41 AM > To: [log in to unmask] > Subject: [TN] PPM calculations > > Dear colleagues > > We have some argues regarding PPM calculations, For an example: for > placement station of automatic SMT components, do we have to count the > soldering pads or only the components. > If only the components its not the same level of difficult for > capacitor > and fine pitch. > The same question is for dispensing machine of SMT glue. > Please E Mail me the general formula for PPM calculation. > > Thanks and Best Regards > > Rokah Reuven > > IPC Member > > ################################################################ > 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 ################################################################