Testing bridges to nowhere - combining Boundary Scan and capacitive sensing

As printed circuit board dimensions continue to decrease, in-circuit tester (ICT) access using a bed-of-nails plus capacitive sensing is increasingly difficult. Stimulus injection using IEEE 1149.1 Boundary-Scan has been proposed as an alternative, but without modification it has significant limitations. An IEEE-supported Working Group is developing an extension entitled, “1149.8.1 - Draft Standard for Boundary-Scan-Based Stimulus of Interconnects to Passive and/or Active Components”. It would add capabilities to 1149.1 that facilitate testing of connections to non-Boundary-Scan components, especially passive components and vacant connectors that are connected to devices equipped with 1149.8.1 facilities. This paper describes existing limitations, IC design changes that would address them, some experimental results, and a summary of how this proposed standard is evolving.