Digitaltest, the developer and supplier of automated test systems for electronic circuit boards, has significantly increased the test options and test coverage of densely populated PCBs with a new process. To enable the testing of a PCB on which some nets could not be reached with tester pins and possible contact pads were difficult to see, an optimum mix of in-circuit, functional and boundary scan tests had to be developed.
Test coverage was increased by having Digital Test use the standardized diagnostic protocol as in their in-circuit test (ICT) in addition to checking the boundary scan capable component. The same function used to send and receive data to the boundary scan cell also stimulates the functionality of the non-boundary scan component by activating the corresponding input on the non-boundary scan component and recording its output signals. Digitaltest engineers were thus able to drastically increase test coverage without having to resort to boundary scan devices from external suppliers and thereby incurring additional costs.
The boundary scan components are controlled via simple commands from the Digitaltest test system's user interface. The tests can be performed by placing a 'virtual pin' between a boundary scan component and a non-boundary scan component in the immediate vicinity. "It's as if we had built our own test drivers and sensors into the integrated circuits (ICs) themselves," says Digitaltest, explaining the concept. This makes it easy to test even the smallest PCBs with limited test access, even if they are densely populated with tiny components.
