PALO ALTO, CA-- Agilent Technologies Inc. (agilent.com) has developed bead probe methodology for in-circuit test of high-speed and high-density printed circuit boards (PCBs). Bead probe technology addresses the needs of electronics contract manufacturers for accurate testing of increasingly complex PCBs, such as those used in communications and computing.

 

As board circuitry gets smaller, traditional bed-of-nails test solutions become problematic. Because on-board test target sizes are shrinking, this approach is no longer capable of reliably contacting hyper-small test targets, which have an unacceptable performance impact on high-frequency signals. Likewise, boundary-scan cannot solve this problem because it does not offer 100% coverage of defects.

 

Bead probe technology circumvents these issues by placing very small, hemi-ellipsoid beads of solder directly onto a board's copper traces. A bead probe, only a few mils tall, protrudes above the solder mask. When partially flattened by a fixture-based, flat-faced target probe, it gives low-contact resistance needed for testing.

 

Bead probes are easily fabricated, using the same steps as solder masking/stenciling.

 

"Bead probes are particularly well suited for highly dense layouts or gigabit signals and, according to our tests, have a negligible impact on circuit performance during normal operation," said Kenneth Parker, engineer/scientist for Agilent's Electronic Manufacturing Test Division. "Bead probes let us approach an ideal of layout-independent, test-point placement -- a great benefit in high-density, high-frequency design that will revolutionize the normally adversarial relationship between board designers and test engineers."

 

Currently being tested by Agilent's high-volume manufacturing partner, full licensing of the technology is expected to be available by mid-2005.

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