An Electromagnetic Sensing Method (ESM) to Detect the Short-Circuit in PCB

Abstract

The short-circuit phenomenon is one common error in the operation of electronic circuit. Short-circuit will cause the electrical components damage and the incorrect function in PCB. In general, the detection of short-circuit is performed by using the electrode probe to contact each pad in single PCB or the probe card in mass production of PCD. Due to the fast development of circuit layout, the size of IC with pads is getting smaller; therefore, it is much difficult to detect short-circuit in PCB by the pads-contact inspection. This paper presents a method to detect short-circuit area in PCB without the use of electrode probe, which employs the electromagnetic signals to sense and identify the change of electromagnetic induced by short-circuit. We design an electromagnetic sensing probe which comprises of an equivalent circuit to detect the change of electromagnetism in PCB, and employ an X-Y table for automatic positioning. Instead of tiny electrode probe manufacturing, the electromagnetic sensing method (ESM) is able to detect the short-circuit area inside the multi-layer PCB. In addition, the inspective module with ESM can be designed to be a portable instrument without the space limitation. The article shows the verification of proposed system with the scanning pitch is from 5 to 20 mil line width, the working distance of sensing probe is from 1 to 20 mm, and 4 layers PCB measurement. We also experiment the real case detection by using the ESM in PCB and display ESM can successful indicate the probable area of short-circuit.