Will Test Compression Run Out of Gas?

Test compression is one of the advancements in scan-based DFT/ATPG that can reduce the manufacturing test cost by significantly reducing both, the test application time and the required tester memory to store test data. It is quite typical to get a test compression ratio of 10-25X for most designs, and up to 100X or more for some of the designs and compression techniques. However, there are some practical and fundamental limits to how much compression can be achieved. To understand these limits, let us first look at how test compression works.