Chip level fault location using X-algorithm

In board level testing the faults are usually isolated to a field replacement unit (FRU) rather than to a single chip. In this paper a new algorithm, called the X-algorithm, is presented to locate a faulty chip in an FRU. The location patterns (LPs) which contain only one symbol X/X¯ are introduced. The trajectory of the X/X¯ propagation sensitises the faults in the FRU. Based on the test results the LPs can be generated easily. In the X-algorithm the X/X¯ propagation trajectory is analysed so that the faulty chip can be located automatically. Preliminary results show that the algorithm is quite effective, and it may not be necessary to exhaustively simulate with the LPs