Detecting the "Undetectable"

In one example, a manufacturer used IR to troubleshoot a "bone" pile comprising boards with specific faults that could not be detected reliably via other methods. The IR system, however, effectively and accurately determined the causes of failure resulting in an 80 percent recovery rate, leading to a savings of $960,000. Another global EMS achieved a 95 percent board recovery rate while reducing debugging time by more than 50 percent. And, during a two-week period, IR screening helped yet another provider recover assemblies generating a savings of $76,000.

In a specific example, ICT board testing exposed a short but could not isolate it. When the assembly was tested with an IR system, however, a hot spot was detected immediately over one of 150 tiny capacitors. Absent IR, this type of short could have taken hours to isolate, if spotted at all. In another case in which more than 100 decoupling capacitors were placed on a single-sided assembly, the product exhibited a 2 percent failure rate owing to component cracking during assembly. The open, which presented possible noise and timing issues that could not be detected with ICT or FT, was located immediately via IR test.

OEMs also can benefit from IR's ability to respond to rework and repair problems associated with multiple revisions of PCBAs in the field. Whereas ICT fixtures typically are reworked to the latest revision, this may inhibit the manufacturer's ability to test field returns that arrive at an earlier revision level. With IR technology, however, a database of good signatures for multiple revisions can be archived economically for quick failure analysis and repair. Therefore, fixture cost and test development efforts can be kept to a minimum.

Conclusion

While IR imaging can address the problem of rework and repair effectively and economically, its benefits do not end there. The technology can be used as a process development tool for inspection and screening "upstream" in the manufacturing line. When used in this context, it shortens time-to-market through a combination of simplified fixturing and shortened set-up and training time, less emphasis on design-for-test, quick fault isolation and disposition, low initial capital investment, and lower operator skill-level requirements for in-line automated testing.