Risks associated with faults within test pattern compactors and their implications on testing

We analyze the risks associated with faults affecting a key component block of today´s DFT structures, that is the compactor. We show that, because of compactors´ internal faults, DFT structures may become useless, with consequent dramatic impact on test effectiveness, product quality and defect level. We borrow the well-known fault secure property for DFT compactors and we show that it guarantees that no escapes or false acceptance of faulty products may occur because of faults within compactors. We discuss the fault secureness of some recently proposed compactors and we provide general design rules to be followed to guarantee fault secureness.