Scan Chain Reordering

What does Scan Chain Reordering mean?

Scan chain reordering refers to the process of optimizing the arrangement of scan chains within an integrated circuit (IC). Scan chains are used during testing to access and control the internal nodes of the circuit, and their placement can significantly impact the performance and efficiency of the testing process.

Scan chain reordering aims to minimize the number of scan patterns required to test the circuit, reducing overall test time and cost. It also helps minimize the number of stuck-at faults that need to be tested, increasing the efficiency and reliability of the testing process. Additionally, optimizing scan chain placement can reduce the need for additional test Hardware, Leading to cost savings.

Applications

Scan chain reordering is a crucial technique in the manufacturing and testing of ICS, enabling efficient and reliable testing. Its applications include:

• Manufacturing Test: Scan chain reordering optimizes test patterns, reducing test time and increasing test coverage during IC manufacturing, leading to higher yields and reduced defect rates.
• Field Testing: Scan chain reordering simplifies field testing of ICs by reducing the number of scan patterns needed and minimizing the need for additional test hardware, making field testing more portable and efficient.
• Low-Power Design: Scan chain reordering can reduce the power consumption during scan testing by optimizing the scanning sequence, reducing unnecessary Switching activities and lowering test power.
• Timing Optimization: By reordering scan chains, it is possible to optimize the timing of scan operations, improving test throughput and reducing test time, especially for circuits with complex timing constraints.
• Design-for-Testability (DFT): Scan chain reordering is an essential part of the DFT process, where it helps improve testability and reduce test complexity, enabling efficient and effective testing of complex ICs.

History

The concept of scan chain reordering was first introduced in the 1980s as a means to improve the testability and efficiency of IC testing. The initial algorithms focused on reducing the number of scan patterns required to test the circuit. As ICs grew in complexity, new techniques were developed to handle larger circuits and optimize for additional factors such as power consumption and timing.

Over the years, scan chain reordering algorithms have evolved significantly, incorporating advancements in optimization techniques, such as genetic algorithms, simulated annealing, and machine learning. Today, scan chain reordering is an integral part of IC design and test methodologies, ensuring efficient and reliable testing for a wide range of applications.