hazard rate

**Hazard rate** is the **instantaneous conditional failure intensity at a given age for units that have survived up to that point** - it is the most direct indicator of current reliability risk and the foundation of bathtub-curve interpretation. **What Is Hazard rate?** - **Definition**: Failure probability per unit time conditional on survival to the present age. - **Units**: Usually reported as failures per hour or FIT for semiconductor reliability contexts. - **Curve Behavior**: Can decrease in early screening phase, flatten in useful life, then rise during wearout. - **Model Link**: Derived from distribution and survival functions in Weibull, lognormal, or exponential models. **Why Hazard rate Matters** - **Real-Time Risk Visibility**: Hazard shows when product population is entering higher-risk lifetime regions. - **Maintenance Strategy**: Guides preventive replacement and monitoring intervals in long-life deployments. - **Design Validation**: Compares expected versus observed hazard evolution to detect model mismatch. - **Warranty Planning**: Hazard trends inform reserve policy and field support forecasting. - **Qualification Focus**: High predicted hazard windows can be targeted with additional stress evaluation. **How It Is Used in Practice** - **Data Estimation**: Estimate hazard from failure-time cohorts with censoring-aware statistical methods. - **Model Fusion**: Combine field, qualification, and monitor data to stabilize hazard estimates. - **Operational Use**: Feed hazard trend into reliability dashboards and lifecycle control decisions. Hazard rate is **the operational heartbeat of reliability engineering** - tracking instantaneous risk over age enables proactive action before failures escalate.