Magnetic In-circuit Testing of Multiple Power and Ground Pins for Open Faults

摘要

The viability of magnetically detecting open faults among multiple power and ground pins of an integrated-circuit package is investigated. The experimental technique is based on injecting current to the leadframe through the chip, and individually sensing the lateral magnetic field of each VDD or GND lead on top of the package. Field distribution in sensor plane is analyzed in order to determine the interference conditions under which correct classification of pin continuity is possible. It is shown that field-based classification benefits from a mildly subtractive interference. Also proposed is a model-based algorithm by which lead currents are calculated from field readings. Classification on the basis of current is shown to be robust against interference. Predictions are verified with experimentation conducted on a PQFP package with a moving Hall sensor.