It is the same for our organisation, please do the same for me. If you
respond directly to the asker, please cc to me. 

Thanks 

>Date: Thu, 10 Jul 1997 08:22:34 +0200
>From: Jos Aarninkhof <[log in to unmask]>
>Reply-To: [log in to unmask]
>Organization: SPA Nedworks
>To: [log in to unmask]
>CC: [log in to unmask], [log in to unmask]
>Subject: PPM defect counting
>
>Hello there,
>
>We are in the middle of  studying how to implement PPM in our
>organisation and are looking for all information which can help us to
>build a good system for defect counting.
>So please keep me posted about all reply's you get. All other
>information would also be welcome.
>
>Thanx,
>
>
>Jos Aarninkhof
>SPA Nedworks Almelo bv
>NetherlandsVickie Chapman wrote:
>> 
>> Rick --
>> 
>> Great question! I wish the industry as a whole would standardize on this! I
>> would be very interested in hearing what other replies you get back.
>> 
>> We count defects basically the same way you do,  but with some variations
>> depending on the defects were tracking:
>> 
>> Solder defect rate:
>> 
>>         # of defective solder joints / total # of solder joints
>> 
>> Placement defect rate or defective component defect rate:
>>         # of defective placements or defective components / total # of
>> components
>> 
>> Total process-related defect rate:
>> 
>>         (# of defective solder joints + # of placement defects) / (total
# of
>> solder joints + total # of components)
>> 
>> Over-all defect rate:
>>         (# of defective solder joints + # of placement defects + # of
defective
>> components) / (total # of solder joints + 2*(# of components))
>> 
>>  Since the "over-all" defect rate includes electrically defective
components,
>> each component has an additional opportunity to be defective.
>> 
>> # of defective solder joints = the number of pins affected. If one whole
side of
>> a 60-pin QFP is shorted together, that's 15 defective solder joints.
>> 
>>  The exception is that if just two pins are shorted together, I suspect
this
>> just gets counted as 1 defect most of the time.
>> 
>> If the QFP is misclocked, that's one defective placement.
>> 
>> If the QFP has an internal defect, that's one defective component.
>> 
>> -- Vickie Chapman
>> 
>> 
>> 
>> On Wed, 9 Jul 1997 10:33:41 -0700 RICK VERNON wrote:
>> 
>> > From: RICK VERNON <[log in to unmask]>
>> > Date: Wed, 9 Jul 1997 10:33:41 -0700
>> > Subject: PPM Defect Counting
>> > To: [log in to unmask]
>> >
>> > We count our defect opportunities as follows: one per component plus
>> > one per solder joint. A resistor would be three defect opportunities,
a 144
>> > pin QFP would be 145 defect opportunities.
>> >
>> > We count actual defects as follows: Tombstone part is one defect.
>> > Insufficient solder on one pad is one defect. Solder short between three
>> > legs of an SOIC is one defect. Skewed SOIC is one defect.
>> >
>> > I have concerns that we are presenting an artificially low PPM rate by
>> > counting defects this way. Others have concern that if we count defects
>> > the same way we create opportunities, the PPM numbers will be inflated.
>> >
>> > I'm looking for info on how others in the industry count actual
defects that
>> > affect more than one opportunity.
>> >
>> > Thanks.  Rick Vernon, QA Manager   [log in to unmask]
>> >
>> >
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>
>
-------------------------------------------------
Patrick Ducas
Process Quality Engineer 
Matrox Electronic Systems Ltd
E-mail: [log in to unmask]
Tél:(514)969-6000 ext.2971   Fax:(514)685-3415
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