Howard:
It depends on the complexity of the board. It could be 0.7,
1.9 or 3.5. One board can have two defects others can have 7 defects and
some none. DPU is a defect average of many boards of the same type. DPUs
can be compared with other groups of boards of the same type. Gauging the
whole shop for quality, a better method can be used, which is DPMO. Using
DPMO all the boards can be put in the metric. Every part that gets placed
by the chip shooter or the pick and place, every solder joint are
opportunities. A DPMO of under 1000 is a good number in my point of view.
Under 500 is great.
Regards,
Ramon
> -----Original Message-----
> From: Howard Watson [SMTP:[log in to unmask]]
> Sent: Wednesday, October 01, 2003 5:22 PM
> To: [log in to unmask]
> Subject: [TN] DPU and PPM
>
>
> Hi everyone,
>
> The upper management team here uses a DPU metric for our board shop, for
> what reason I am trying to comprehend. Basically, one solder joint defect
> on a board equates to the whole board counting as a defect. The
> opportunities are irrelevant - every board gets one opportunity. When the
> "PPM" numbers are published, which is what they call them, they are
> outrageously high. My questions are:
> Does anyone use Defects per Unit at the board level?
> If so, what kind of numbers are you seeing.?
>
> I am pursuing a change to use real DPMO metrics, but so far I've been
> unsuccessful. I even presented IPC-7912, but it was ignored. Thanks in
> advance for the help.
>
> Howard Watson
> SMT Manufacturing Engineer
> AMETEK/Dixson
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