The Increasing Importance of Utilizing Non-intrusive Board Test Technologies for Printed Circuit Board Defect Coverage

As printed circuit boards have decreased in size and increased in complexity (i.e. number of layers, number of installed components, speed of busses, etc.), access to test resources (i.e. probe points) necessary for sufficient printed circuit board test has diminished. The use of intrusive test methods such as in-circuit testers, manufacturing defect analyzers, and flying probe testers entails many downsides. Each method requires access to printed circuit board probe points, the equipment necessary to facilitate each intrusive method can take up large amounts of floor space in a manufacturing facility and can be costly to operate and maintain (i.e. technician time, fixture origination and fixture revision due to printed circuit board redesign). Because of these and more downsides, non-intrusive board test has emerged as a cost-effective alternative to intrusive test or as a cost-reducing complement where intrusive test methods are still used.

I. Introduction

The non-intrusive board test (NBT) methodology integrates several, software-driven, test technologies to restore test coverage lost due to diminished printed circuit board (PCB) physical access and reduce cost where intrusive methods are still used[1]. The non-intrusive test technologies that make up NBT include, but are not exclusively limited to, boundary-scan test (BST), per IEEE Std. 1149.1 and its progeny, processor-based functional test (PFT), employing processor-based target agents to test on-board memories and high speed end-point components, and FPGA-controlled test (FCT), deploying FPGA-based embedded instruments for component functional and performance test. In fact, these technologies form a perfect complement. They are all non-intrusive, typically requiring access only to the common board level debug/test access port; but each test technology brings its own distinct elements of defect coverage to the NBT strategy. These complementary test technologies provide PCB defect coverage in three critical areas: structural test, functional test, and performance measurement.