Rich,

     PPM is a metric that one company uses to measure
another company's quality performance. 25 is a very
tough number to meet but not impossible as this is the
quality of the delivered product.

   In terms of in-process performance it is a very
difficult "number" to achieve. However PPM is not an
in-process metric. In-process you should use a
similiar metric called Defects Per Million
Opportunitites. This is a calculation that essentially
levels the playing field from one product to another
by taking in each product's level of complexity.

    The key is to have an accurate denominator for the
DPMO measurement. The methodology I have used in the
past goes like this for an mixed technology module
line.

PWB = 1

Bar Code labels = 2

Glue dots = 1 for each component

Component counts = top and bottom side

Solder Joint Count = top and bottom side

Though Hole Device Count = top and bottom side

Wave Solder Joint Count = bottom side

Postwave hand assembly part & joint count

In Circuit Test (ATE) = 1

Functional Test = 1

Audit = 1

These are divided throughout their respective process
steps and are never double counted. Where you lump
them together is up to you depending upon where you
have your inspection points. You would also use them
in unison to look a given products total quality
level. Also at ATE and Functional test yields are a
better way of looking at those specific steps.

The 25 DPMO metric for a Module line is a tough metric
to beat unless you have a "HUGE" denominator. For
example a 26 ppm requires that you have no more than
400 defects in 15 Million opportunities.

Finally in terms of qualifying equipment, I would not
put much weight on a ppm number but would look to Cp &
Cpk numbers as these a the true measurements of a
piece of equipments capabilities.

Hope this helps,

Tony Di Mauro
Quality Engineer
Circuit Technlogy Center - Haverhill MA
--- Rich Lasko  wrote:
> Good Morning Tech Group,
>
> We have a customer that is a Tier 1 supplier to the
> automotive industry.  We
> are a subcontractor to them.  They are taking the
> QS9000 quality standard
> and applying it on us.  They have also advised us
> that they are looking for
> a 25 PPM (parts per million) on all of their
> electronics assemblies we make
> for them.  My question is this, is there a
> documented PPM study or survey
> that was completed for the electronics industry?  Is
> the 25 PPM an realistic
> goal?  Some of our machines that are brand new are
> spec'd to have a 200 PPM
> "out of the box".  If this is the case...then
> obtaining 25 PPM would seem
> almost impossible without redundant inspections.
>
> If there is anyone who could assist me in this, I
> would really appreciate
> it.
>
> Rich Lasko
> Quality Manager
> Badger Electronics
> (262) 886-8800 Phone
>
>
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