ASSET Boundary-Scan Test And Flying Probe Tester Minimize The Use Of CCA Functional Test For Defense Communications Vendor

A manufacturer of communications boards for defense and commercial applications has all but eliminated the need for digital-CCA functional test by teaming the ASSET boundary-scan test and in-system programming system with a flying probe tester from DiagnoSYS Ltd.

"Why do functional test when our yields are 95 percent or more after doing boundary-scan and flying probe testing?" the firm's test manager asked. "For our low volumes, we had a hard time justifying the extra time to generate and perform functional tests and the added expense of a VXI test fixture. This new near-functional-test philosophy works well for us."

The company began using ASSET and the Autopoint Flying Prober from DiagoSYS several years ago. At the time, they were using VXI-based automated test equipment (ATE) and were not satisfied with the results. Despite the increasing complexity of many of the firm's designs, the move to boundary scan testing and the use of ASSET have reduced initial debug and manufacturing test time dramatically. In contrast to the trend they were experiencing using ATE functional test, using PC-based boundary-scan test combined with a flying prober have proved a very cost- and time-effective solution for digital board test.

A typical scenario for the firm's test department goes something like this. A video transmission board designed, manufactured and tested by the company might be a VME board containing 16 or more high-density field programmable gate arrays (FPGAs) with components on both sides of the board. Before boundary-scan and flying probe tests were implemented by the firm, the initial debug process would take anywhere from five to six weeks. Now, using ASSET the company is able to bring up newly designed boards in approximately three days. The subsequent test flow involves using the Autopoint to do a power-off MDA (manufacturing defects analysis) test for defects associated with digital, discrete, and analog devices (the MDA requires a known good board to generate a test), followed by boundary-scan testing on the boards.

Several different formats of communications cards are designed by the company, including VME, VME64x, PCI and CompactPCI. While a new design is being developed and manufactured for the first time, boundary scan tests are being developed in parallel using ASSET. The goal of the test group is to have a boundary scan test suite available by the time the first board is assembled in manufacturing. In this way, that test can be used for the critical initial debug of boards when they first start coming off the manufacturing floor. The shorter debug/test phase made possible by ASSET and the DiagnoSYS flying probe tester mean that the firm's products are now being delivered ahead of schedule.

Over the last couple of years, test engineers at the company have been able to use the ASSET system to improve test coverage by developing special sets of macros which are used to drive tests through areas of the boards that are not equipped with boundary scan cells. Engineers have also designed a special universal adapter for their flying probe tester so that boards ranging in size from 3"x 3" to 20"x 20" can be tested. Test coverage is also increased by the fact that, using standardized VME/PCI/CPCI fixtures running small board-unique daughter cards, the company is able to originate boundary-scan signals off-board, drive test signals onto the board-under-test and then route them off the board again. This tests the I/O portion of every board, including all connectors. The firm's test manager estimates that this procedure increases a board's test coverage by more than 20 percent.

The company has also begun using the ASSET system to dynamically load programmable devices after they have been inserted onto a board in assembly. The firm has simplified its manufacturing flow by loading programmable devices immediately following board test, and reduced redesign costs associated with firmware updates.

Based on its past successes, engineers at the company are now looking into using ASSET and boundary scan to perform system level tests on projects that are currently being designed. The goal is to have a complete Compact PCI system that is fully testable using ASSET, including tests that would transverse the system's backplane.

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