Chapter 23
Contactless Testing and Diagnosis Techniques
23.1 Introduction
With decreasing feature size and increasing chip densities, the classical mechanical probe approach for internal fault detection and functional testing faces increasing challenges. Mechanical probes have limitations because of their relatively large size and inherent parasitic effects. The Semiconductor Industry Association's 2009 International Technology Roadmap for Semiconductors (ITRS) predicts that ASICs will require more than 5000 I/O pads for the next three years, with a peripheral pitch distance of 
[1]. Large-chip I/O pad counts challenge testing reliability in numerous ways; for example, assuring reliable ohmic contact using tiny needle probes to all test pads during repeated die tests becomes a significant concern.
Designs for testability approaches are valuable techniques for helping solve the growing test problem. However, as the ITRS suggests, they alone do not offer a solution.
These factors encourage developing nonmechanical techniques for debugging and design verification, as well as for functional testing. Contactless testing and diagnostic measurement methods can address the difficulties associated with mechanical probing.
A number of contactless techniques have been investigated over the years especially since the 1980s. Industry has used ...
