Question 1

How do I define 'opportunities' for DPMO calculation?

Accepted Answer

An opportunity is any measurable characteristic on a unit that could potentially be defective. Count only independent opportunities that are meaningful to the customer. For a solder joint, opportunities might include: position, wetting, bridging, and void — but typically each joint is counted as one opportunity. Be consistent across time periods for valid trend analysis.

Question 2

What is the relationship between DPMO, PPM, and DPU?

Accepted Answer

DPU (Defects Per Unit) = total defects / total units. PPM measures defective units per million units. DPMO measures defects per million opportunities. If a unit has only 1 opportunity, DPMO = PPM. For multiple opportunities: DPMO = DPU / opportunities × 1,000,000. DPMO is always ≤ PPM when opportunities > 1.