Definition DPMO and PPM - Differences - Defects Per Million Opportunities and Parts Per Million?

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W

wmarhel

#2
jackylpt said:
Does anybody know what is difference between DPMO and PPM? thanks.
DPMO = Defects per Million Opportunities

PPM = Parts per Million (could also be DPM)

Think of PPM/DPM as a binary result, it is either a PASS or FAIL condition. A unit/part/service is acceptable to the customer, or it isn't. So if 10 units out of a hundred failed, your PPM would be: (10/100)*1,000,000 = 100,000 PPM.

DPMO is looking at opportunity failures. In this instance, each unit could potentially fail from 10 different causes. I'm not a huge fan of this line of thinking except when looking at it from a design/new product introduction standpoint. Here's a thread where there is more discussion on the topic:
DPMO for Testing Stations.

Wayne
 

Statistical Steven

Statistician
Staff member
Super Moderator
#4
wmarhel said:
DPMO = Defects per Million Opportunities

PPM = Parts per Million (could also be DPM)

Think of PPM/DPM as a binary result, it is either a PASS or FAIL condition. A unit/part/service is acceptable to the customer, or it isn't. So if 10 units out of a hundred failed, your PPM would be: (10/100)*1,000,000 = 100,000 PPM.

DPMO is looking at opportunity failures. In this instance, each unit could potentially fail from 10 different causes. I'm not a huge fan of this line of thinking except when looking at it from a design/new product introduction standpoint. Here's a thread where there is more discussion on the topic:
DPMO for Testing Stations.

Wayne
So another way of saying it is DPMO = PPM/# of opportunities per part?
 
J

jenik - 2009

#6
Re: DPMO and PPM - Differences => impact to the test coverage

Can you propose how to display dpmo and/or ppm in the Test Coverage report (In-Circuit test) intead of percentage (ie. dpmo / ppm for each device)?

Let's assume 1 component (capacitor) 'C123' assembled on the pcb (device package 0603 = 2 terminations) with an another 15 capacitors (total 16 cap's) with same package (and same PN) . There are 67 populated component and 509 terminations in total on the PCB.

The Component Opportunity for 'C123' Oc=1 + 1board = 2
Terminations opportunity Ot = 2
Placement opportunity Op = 1

C123 test coverage is 80% (used deduction method), because of cap value, tolerance and parallel connection.
C123 is accessible from both side, ie. 100% connection.

Can you propose the equation for calculating for both DPMO and PPM?
Can you evaluate which index is better to be used (dpmo or ppm)?
We do have a target from our customer 500 DPPM. Can you suggest how to calculate PCB overall (dpmo or ppm) in purpose to compare / determine whether we are on the target?

Any sugestions welcomed - Thanks.
Jan
 

Marc

Hunkered Down for the Duration with a Mask on...
Staff member
Admin
#7
Re: DPMO and PPM - Differences => impact to the test coverage

I know this is an old one, but can anyone help with an answer to Post 6 by jenik in this thread? My Thanks in advnce!
 
B

BridgeGap

#8
Re: DPMO and PPM - Differences => impact to the test coverage

Hello Jenik,

I am not an engineer nor am I in the PCB business. However, I will provide you with my thoughts on the direction you might take to get the answers to your questions.
1. Because your customer uses PPM (I am assuming DPPM is the same), then you would want to track that way at minimum. Consider, however, that they may reject parts that are not necessarily defective. Not sure if they allow you the opportunity to get an actual or true defective count. Cosequently, I would be careful about using this as an internal metric.
2. How does the customer determine and classify defectives?
3. There may be value in going to DPMO for your internal quality metric.
3. How does the tester determine defects? Perhaps you could look over the history of test results and assign a value to "opportunities" based on the total number of different defect locations on the part.

Just some quick, off the top thoughts. If your still interested in an answer, hopefully this will move the discussion along and get you what you are looking for.
 
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