DPMO - Defects per Million Opportunities
Specified by IPC-7912 three calculations:
termination opportunities
placement opportunities
component opportunities
For termination opportunities add up the number of solder joints for a
board, multiply by the number of boards built to get the total number of
opportunities. Divide the number of termination defects identified by
the total number of opportunities and multiply by 1 million to get
DPMO.
Perform a similar calculations for placement opportunities (count all
components except the board), and for component opportunities (count the
board as well). We combine component and placement opportunities in our
calculations so we don't follow IPC-7912 exactly.
For further info order a copy of IPC-7912 from IPC.
Blair
>>> [log in to unmask] 10/02/03 09:34AM >>>
Ramon,
Can you expand a little on DPMO? What is measure and how is it
calculated?
Thanks
Eric
-----Message d'origine-----
De : TechNet [mailto:[log in to unmask]] De la part de Dehoyos, Ramon
Envoyé : 2 octobre, 2003 09:17
À : [log in to unmask]
Objet : Re: [TN] DPU and PPM
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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