scan compression

**Scan compression** is **a technique that reduces scan test data volume by compressing stimulus and responses** - Decompressors expand tester patterns on-chip and compactors fold responses back to limited tester channels. **What Is Scan compression?** - **Definition**: A technique that reduces scan test data volume by compressing stimulus and responses. - **Core Mechanism**: Decompressors expand tester patterns on-chip and compactors fold responses back to limited tester channels. - **Operational Scope**: It is used in semiconductor test and failure-analysis engineering to improve defect detection, localization quality, and production reliability. - **Failure Modes**: Over-aggressive compression can reduce diagnostic resolution and increase unknown-value sensitivity. **Why Scan compression Matters** - **Test Quality**: Better DFT and analysis methods improve true defect detection and reduce escapes. - **Operational Efficiency**: Effective workflows shorten debug cycles and reduce costly retest loops. - **Risk Control**: Structured diagnostics lower false fails and improve root-cause confidence. - **Manufacturing Reliability**: Robust methods increase repeatability across tools, lots, and operating corners. - **Scalable Execution**: Well-calibrated techniques support high-volume deployment with stable outcomes. **How It Is Used in Practice** - **Method Selection**: Choose methods based on defect type, access constraints, and throughput requirements. - **Calibration**: Tune compression ratio against coverage, diagnostic quality, and X-tolerance limits. - **Validation**: Track coverage, localization precision, repeatability, and field-correlation metrics across releases. Scan compression is **a high-impact practice for dependable semiconductor test and failure-analysis operations** - It cuts tester memory and test time for large designs.