A built-in electrical test circuit for detecting open leads in assembled PCB circuits

Abstract

In this paper, a built-in electrical test circuit is proposed to detect an open defect at an interconnect between a land on a printed circuit board and an IC. The test circuit is made of an integrating circuit, nMOS switches and a switch control circuit. A time-varying signal generated by the integrating circuit is provided to a targeted interconnect as a stimulus signal in the tests. An input buffer gate in an IC is utilized as an open sensor in the tests. The open defect is detected by means of supply current of the sensor. We examine by Spice simulation whether open defects can be detected by using the test circuit. The results reveal us that an open defect can be detected at a test speed of 50 kHz for each input terminal of an IC.