Rich;

  In my humble opinion 25 ppm is not realistic for brand new machine and try
to imagine for old equipment.
  One thing you could do is correlate PPM numbers with product yield to see
if all investments to keep 25ppm will be cost effective.
  Let me try explain using numbers

  25 ppm means 1 failure within 40000 placements

  Board A has 50 components
  Board B has 1000 components

  40000/50 = 800 with 40000 placements you assemble 800 boards A
  40000/1000 = 40 with 40000 placements you assemble 40 boards B

  With 40000 placements I will have one failure, so one board bad.

  The yield for Board A is 99,875% ( one failure within 800 boards )
  The yield for Board B is 97,500% ( one failure within 40 boards )

  As you could see the yield is different from both boards but the ppm is
the same, then you could ask for a yield and do the reverse way and find the
ppm needed for that and based on that numbers and real machines ppm you can
certify that your process is/isn't able to achieve the requirements and you
will/won't need investment.
  Managers generally don't known this correlation between boards/ppm/yield
and will always ask why board B is worst than board A, they will
congratulate you about board A yield and complain with you about board B
yield, but both boards are under the same process of 25 ppm !!!

I hope this help

Jorge Dourado de Santana
Maintenance / Process Engr
Microtec - Brazil


> -----Original Message-----
> From: Rich Lasko [SMTP:[log in to unmask]]
> Sent: 25 de Abril de 2000 14:35
> To:   [log in to unmask]
> Subject:      [TN] PPM values for the Electronics Industry
>
> 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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