The intent of this paper is to present several case studies that highlight different analytical methods used to isolate short circuits within Circuit Card Assemblies (CCAs). When working with CCAs, each investigation may present its own unique challenges that can be solved utilizing a diverse toolset. This toolset does not just include test equipment but rather a catalog of methodologies and processes, which is learned through experience while leveraging how others have approached similar problems.

The focus of this paper is to present an interesting case study involving Vishay wire-wound (WSC model) resistor failures, which affected a significant number of production and fielded assemblies. The failures were considered “mission critical”, which was the primary driver necessitating root cause analysis. A disciplined approach to the failure analysis effort was established, which resulted in root cause determination and the generation of appropriate corrective actions. This paper will highlight a non-conventional decapsulation method used to preserve the integrity of the fragile resistive element and a “lucky break” that was instrumental in linking the supplier’s actions to the failures.

Time Domain Reflectometry (TDR) is an analysis technique for characterizing a transmission environment (PCB traces, cable assemblies, etc.) and identifying the physical location of defects or impedance discontinuities which can quickly narrow the focus of an investigation. This paper introduces the capability and presents several case studies spanning different applications where TDR was useful as a non-destructive analysis technique.