Opportunity count methodologies define how FactoryLogix counts and calculates the number of opportunities in an assembly where a defect or other problem might occur. This calculation is used to generate Defects Per Million Opportunities (DPMO) reports and charts in the Analytics client application.

PPM versus DPMO

• Parts Per Million (PPM) is a quality measurement indicating the number of defective assemblies per million produced.
  
  For example, if you have 25 defective pieces in a shipment of 1,000 pieces. 25/1000= .025 or 2.5% defective. . 025 X 1,000,000 = 25,

• 000 PPM.
  

• DPMO is a more accurate, “weighted” metric that considers the complexity of the manufacturing process.
  

• 
  To calculate DPMO, you take the number of defects divided by the number of defect opportunities, multiplied by 1,000,000.

DPMO Example

• Example Board A is a computer Memory Module with 61 placements
  

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• Example Board B is a computer Motherboard with 3,492 placements
  

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• The total opportunities for Examples A and B are shown for all population points: a routing station where parts are actually placed/inserted on the PCBs. In this example, a mere three defects found on one assembly per job will result in significantly different end-product DPMO calculations (IPC-7912A) for the two PCBs. Assuming a job quantity of 10 boards in each case, the DPMO results would be:
  

  • Example Board A: DPMO = (3/(10*835))*1000000. End-Product DPMO:

• •  359.3

  • Example Board B: DPMO = (3/(10*22660))*1000000. End-Product DPMO: 13.2

IPC-7912A (End-Product DPMO)

• Calculation of DPMO for an End-Item (Finished Product)

• Does not account for Model Point Assignments - considers all parts in CAD

IPC-9261 (In-Process DPMO)

• Calculation of DPMO for each process in the route

• Accounts for Model Point Assignments and No-Pops

• Considers chargebacks in defect collection in order to assist in determining the root cause of a defect

• Provides clear indication of processes in need of improvement

Chargeback example

In this example, using In-Process DPMO (IPC-9261), the specific processes likely responsible for the defects in question are indicated. For this example, assume 1000 opportunities and a Job Quantity of 10. The DPMO results are shown in the following illustration.

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