Abstract

Surface Mount Technology (SMT) ceramic capacitors are widely used on virtually every type of electronic product. In computer systems, SMT capacitors populate the majority of electronic parts found on each Printed Circuit Assembly (PCA) within the product, primarily as bypass or coupling devices between power and ground. As such, the opportunity for failure is substantially higher than with other commonly used active or passive components. Additionally, the relatively small ceramic bodies are prone to mechanical damage. Their proportionately high numbers, sensitivity to mechanical stress and difficulty in isolating to a specific failing device on the PCA (since many of these parts are in parallel with many other identical capacitors) all combine to make the successful isolation and analysis of the root cause of failure particularly difficult for the failure analyst. Often, the cause of failure is misdiagnosed, or the evidence is compromised by the methods used to perform the analysis. This paper will discuss the common failure mechanisms associated with SMT ceramic capacitors, as well as some innovative non-destructive isolation tools and techniques, including C-Mode Scanning Acoustic Microscopy (C-SAM), Infrared thermography (IR) and Micro-Focus X-ray analysis. Several case studies will be cited which demonstrate each of the mechanisms and methods. Additionally, the processes used to properly analyze these defects will be examined.

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