Contactless current measurements using a needle sensor

We present an improved method for measuring currents in packaged integrated circuits (IC) for the purpose of test and failure analysis. We use a quartz resonator, called needle sensor, to detect the magnetic field of the device under test (DUT). Thus, the measurement principle is similar to conventional magnetic force microscopy. Compared to a cantilever-based scanning force microscope the advantage of a needle sensor is the much easier test access because of its geometry. With this probe we realized current measurements with a sensitivity of 100 μA. The results are verified by using a simple model describing the basic principle of our measurement setup.