Time domain reflectometry (TDR) is widely used to measure the electrical length of conductors. It has also proven useful for isolating failures in ICs. This article describes a variation of the method, called comparative TDR, that overcomes inherent timing limitations and simplifies use. It discusses the basic hardware requirements of the new technique and presents examples demonstrating its use on opens and shorts in ceramic flip-chip packages.
Time Domain Reflectrometry or TDR is an analytical technique used to determine the impedance and electrical length of conductors. This relatively inexpensive technique utilizes a pulse card and digital oscilloscope whereby the reflected signal amplitude from an initiating pulse is measured versus time. The technique is useful for characterizing the impedance of a conductor in the time domain, and has traditionally been employed in board level analysis. More recently, TDR has been shown to be useful in electrically isolating integrated circuit package failures1. Historically, open failures on non-flip chip devices were resolved through relatively straight-forward, low risk methods in a failure analysis lab. Typically, root cause analysis involved simple verification on a curve tracer, non-destructive inspection using X-Ray imaging, chemical, thermal or mechanical decapsulation, optical and electron microscopy and as necessary, the use of mechanical probe isolation. The implementation of advanced flip chip package technology rendered the traditional isolation methodologies inadequate. After verification and X-ray inspection, a decision had to be made prior to subsequent destructive physical analysis as to the most probable failure location. Since the board interconnects, board interposer, and bump locations were not geometrically aligned, isolation of opens through physical cross-sectioning became risky, tedious and lengthy. These constraints were overcome through the use of TDR analysis. The authors have successfully incorporated the TDR technique into AMD’s microprocessor failure analysis flow, improving success rate, reducing risk and decreasing turn-around time. The paper will include a brief description of TDR theory and hardware, technical barriers that the authors encountered during implementation, sample preparation as well as details where the technique was successfully employed in failure isolation. The remaining portion of this paper provides illustrative examples where TDR was effectively utilized in the analysis of slot A cards, ceramic flip chip PGA pins, and internal package trace failures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.