An Investigation into the Failure Characteristics of External PCB Traces with Different Angle Bends

Abstract

The design of a Printed Circuit Board (PCB) involves satisfying numerous design constraints in terms of the positioning of components and the routing of conducting tracks or traces between components. One common design constraint is limiting the maximum angular bend that a trace can make (e.g. to 45°) for several potential reasons including reliability. In this paper, we systematically investigate the failure characteristics of PCB external traces with different angle bends to understand the implications in a modern context with modern PCB manufacturing processes. This involves destructive testing of straight traces with no bends, traces with only 45° bends and traces with only 90° bends. There are three aspects to the testing: (1) maximal current testing, in which the maximum current that a trace can withstand before failure is measured, (2) failure location testing for traces with bends i.e. trace failed on straight segment or at the bend, and (3) time to failure testing. We did not find a large difference between the maximum currents that can be withstood by straight traces, traces with 45° bends and traces with 90° bends. However, some of the interesting results are that traces with 45° bends are significantly more likely to fail at the location of a bend than traces with 90° bends, and straight traces take much longer to fail on average than traces with bends for a given test current.