Diminishing ICT Test Coverage

Our chief technologist of non-intrusive board test, Adam Ley, recently published an e-Book on solving the problem of diminishing test coverage from In-Circuit Test (ICT). What’s the key take-away from this publication?

If you know Adam Ley, you know that he knows his stuff. He’s had an active role in all things JTAG over the last 15 years, having participated in virtually every related standard, including IEEE 1149.1, 1149.4, 1149.5, 1149.6, 1149.7, 1500, 1532, 1581, P1149.1.1, and P1149.8.1; not to mention his contributions to industry forums such as iNEMI, PICMG, and SJTAG. When Adam writes on a topic, you know that it’s well thought-out and comprehensive.

In his e-Book, Adam covers some of the well-known technical issues with ICT, such as increasing circuit density, problems from board strain, EMI, and via stubs’ impact on high-speed I/O. A brief look at the economics of ICT versus its software-based alternative, non-intrusive board test (NBT), is accompanied by a technical overview of the latter’s fusion of structural, functional and performance-based test technologies. 

One of my favorite examples in the paper references the negative impact that ICT test probes can have on press-fit connectors such as DIMM or PCI Express. In the figure below, the counterforce exerted by the test probe loosens or even dislodges the press-fit pin from the circuit board. This can have a horrible effect on system signal integrity, performance and operation.