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
>
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