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

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.