Terahertz and laser imaging for printed circuit board failure detection

This paper describes research and development efforts in the application of advanced optical techniques for prognostic analysis of printed circuit boards and their components. Current methods of automated electronic testing require development of costly unique test program sets (TPSs) for each type of board, and only return information related to the current performance characteristics. The use of laser diagnostics in circuit board testing can eliminate the need for TPSs, while identifying compromises in material integrity that leads to hard and soft component failures. Additionally, they may be applied to solve instances of retest OK (RTOK) and no-fault-found events. Our investigation has focused on terahertz (T-Ray) imaging, laser acoustics, and near-infrared (NIR) laser imaging. T-Ray imaging is an emerging laser-based technology characterized by the ability to "see through" layers of plastic to the embedded metal traces of a circuit board or to the die of an encapsulated microchip. Laser acoustics may be applied to monitor the integrity of solder joints, and NIR laser imaging may be used to identify damage within an integrated circuit (IC). We present the results of our investigation into the combined use of these techniques for fault diagnosis, as well as their relative potential in the electronics test industry.