Enhanced Package Fault Isolation Method Using Time Domain Reflectometry (TDR) Incorporation with Mathematics

Time domain reflectometry (TDR) has gained attention in electrical verification for electronic components over the years. TDR works by sending a series of short pulses through a transmission line under investigation, and measures the reflections that result from a signal travelling through a transmission environment. [1], [2] It is often being used for short or open failures defect localization, to isolate whether the short/ open failure is in the die region or package region. With the enhancement of process technology and increase of layers in the package/ silicon die, and due to limitation of reference medium, the results produced by using TDR can only be used as a rough guide, i.e. based on the TDR results, we can only narrow the open/ short failure to be in the die or package, we could not tell which layer of package the short/open is. This paper demonstrates some successful cases with the incorporation of mathematics together with the use of TDR machine. Open failure can be accurately localized down to specific substrate layer via mathematics calculation. Physical failure analysis further confirmed the accuracy of this method by showing the defect at that specific layer in those cases.