Improving compressed test pattern generation for multiple scan chain failure diagnosis

To reduce test data volumes, encoded tests and compacted test responses are widely used in industry. Use of test response compaction negatively impacts fault diagnosis since the errors in responses due to defects which are captured in scan cells are not directly observed. We propose a simple and effective way to enhance the diagnostic resolution achievable by production tests with minimal increase in pattern counts. In this work we present experimental results for the case of multiple scan chain faults to demonstrate the effectiveness of the proposed method.