Читать книгу Design for Excellence in Electronics Manufacturing - Cheryl Tulkoff - Страница 18

Desired lifetime and product performance metrics must be identified and documented. The desired lifetime may be defined as the warranty period or by the expectations of the customer. Some companies set reliability goals based on survivability, which is often bounded by confidence levels such as 95% reliability with 90% confidence over 15 years. The advantages of using survivability are that it helps set bounds on test time and sample size, and it does not assume a failure rate behavior (decreasing, increasing, steady‐state).

Reliability goals and requirements address the product or system itself and include test and assessment requirements and associated tasks and documentation. These are included in appropriate system/subsystem requirements and specifications, test plans, and contract statements.

Examples of reliability goals and metrics:

 Minimum required field service life under defined conditions: 10 years of environmental exposure and 150,000 miles (or 1 million operating hours)

 Maximum allowable quality defect rates– Field infant mortality quality defect rates at 3‐6‐9‐12 months– Dead on arrival (DOA) defect rate– Required minimum field reliability at one year or the end of the warranty period– Six Sigma first‐pass quality yield– Non‐repairable or failure to replicate (no trouble found, NTF) rates