Boundary scan-the ATE vendors´ view

The author discusses boundary scan which incorporates the use of special components which are linked together to allow access to the internal nodes of a printed circuit board (PCB) without the need to make physical contact through a bed of nails fixture. Boundary scan is one solution for the process verification of highly integrated digital boards where node access is impossible because of extensive use of square mesh tracking and double-sided PCBs. the efficiency of the diagnostic algorithm may be greatly enhanced if there is an understanding of the scan chain profiles. Preferential probing of key pins may allow any chain breakdown to be analyzed. Also, using a fault dictionary approach, reasoned deductions from the scan chain point of failure will allow diagnoses to be proposed about nonprobed areas of the board