Embedded Testing in an In-Circuit Test Environment

In-circuit test (ICT) has been used for more that 30 years to test for correct assembly of components on to a printed circuit board (PCB). The premise behind the in-circuit test philosophy was based on gaining netlevel access to a circuit and driving and sensing signals through the components of that circuit to determine if the components were placed correctly and soldered correctly to the board. Given today's board density and speed requirements, it is becoming more and more challenging to gain access to all of the nets on a given printed circuit assemble (PCA). Even with 100% access, the tester may not be capable of testing all of the nets on a large, high density PCA (due to the sheer number of nets on the board). In addition, as more and more logic is integrated into devices and signal integrity begins to dominate interconnect as the primary board level concern; the "relevance" of in-circuit test seems to be diminishing. This paper will discuss the application of "advanced" in-circuit test techniques to help improve the effectiveness of the in-circuit test on large, fast, complex PCAs with limited (test point) access.