Understanding Process Yield: First Time Yield (FTY) vs Rolled Throughput Yield (RTY)

Introduction

Process yield is a critical metric in manufacturing and quality control. It measures the proportion of products that meet quality standards during the production process. Two common metrics used to assess process yield are First Time Yield (FTY) and Rolled Throughput Yield (RTY). This article will explain how to calculate these metrics and highlight their importance in understanding and improving manufacturing processes.

Process Yield

Process yield refers to the proportion of products that meet quality standards out of the total products produced during a manufacturing process. It is a key metric in quality control and process improvement as it helps organizations understand how effectively they are converting inputs into acceptable outputs. [Keyword: process yield]

First Time Yield (FTY)

First Time Yield (FTY) measures the percentage of products that are manufactured correctly the first time without any rework. FTY is calculated using the following formula:

FTY Number of Good Units Produced / Total Units Produced

Example of FTY Calculation

If a factory produces 1000 units, and 950 of them are deemed good, the FTY would be:

FTY 950 / 1000 0.95 or 95%

Rolled Throughput Yield (RTY)

Rolled Throughput Yield (RTY) takes into account the yield at each step of the process and is a more comprehensive measure as it reflects the cumulative yield across multiple steps. RTY is calculated using the formula:

RTY ∏i1n Yi

Where Yi is the yield of each individual step in the process, and n is the total number of steps.

Example of RTY Calculation

Consider a process with three steps where the yields are:

The RTY would be calculated as follows:

RTY 0.90 x 0.95 x 0.85 0.72675 or 72.68%

Summary

FTY focuses on the percentage of good units produced without rework. On the other hand, RTY provides a more holistic view of the process by considering the cumulative effect of yields across all steps. Both metrics are valuable for assessing and improving manufacturing processes, but they serve different purposes in quality control and process optimization.

Calculating Process Yield

Calculate First Time Yield (FTY) by dividing the number of good units (excluding any rework or scrap) by the total number of units going through the process. Alternatively, calculate Rolled Throughput Yield (RTY) by multiplying the passing rate of all steps within the process together.

Example Circumstances:

Consider a scenario where a process operates at a 95% first-pass yield rate but has a rolled throughput yield of just under 60%. This discrepancy suggests that issues at later stages of the process are significantly affecting overall yield. Fixing these issues can dramatically improve the overall RTY.

RTY can be perfect (100%) if each step in the process is 100% successful, but in real-world scenarios, it is often lower due to failures at different stages.

By understanding the differences between FTY and RTY, manufacturing organizations can better identify and address areas for improvement in their production processes, ultimately leading to higher yields and better quality products.

Conclusion

Process yield is a vital metric in manufacturing that helps organizations measure and improve the efficiency and quality of their production processes. By using First Time Yield (FTY) and Rolled Throughput Yield (RTY), companies can gain insight into the success rates of individual steps and the overall process, enabling them to make informed decisions to enhance their operations.

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