first pass yield (fpy)

**First Pass Yield (FPY)** is the **percentage of devices passing test on the first attempt without rework or retest** — a key manufacturing efficiency metric, with higher FPY indicating better process control and lower manufacturing costs. **What Is FPY?** - **Definition**: (Units passing first test / Total units tested) × 100%. - **Measurement**: Yield without any rework or retest. - **Typical Values**: 85-98% depending on maturity and complexity. - **Goal**: Maximize FPY to reduce cost and cycle time. **Why FPY Matters** - **Cost**: Rework and retest add significant cost. - **Cycle Time**: First-pass success means faster throughput. - **Process Health**: High FPY indicates stable, capable processes. - **Capacity**: Higher FPY means more effective capacity. - **Quality Indicator**: Correlates with field reliability. **Calculation** ```python fpy = (first_pass_units / total_tested) * 100 # Example: 9500 pass / 10000 tested = 95% FPY ``` **FPY vs Final Yield**: FPY measures first attempt only. Final yield includes units that pass after rework/retest, so Final Yield ≥ FPY. **Improvement Strategies** - **Process Control**: Reduce variation through SPC. - **Defect Prevention**: Fix root causes, don't just catch defects. - **Equipment Maintenance**: Prevent tool-induced defects. - **Material Quality**: Ensure high-quality incoming materials. FPY is **the efficiency metric** — high FPY means doing it right the first time, minimizing waste and maximizing profitability.