On-board 3D assembly, multi-layer and micro processing mounting technology is advancing with the miniaturization, high functionality, and high integration of electronic devices. Due to the enhancement of mounting technology on boards, electrical defect modes are getting more diverse and complex than ever before, and in identifying defect locations, in the process of feedback to the early phase of production division, it is necessary to proceed with non-destructive analysis in highly accurate and rapid analysis work.
In this paper, a high-resolution TDR (Time Domain Reflectometry) measurement system was used with the use of electro-optical sampling technology in Advantest's TS9001 TDR system, and a method was used for analyzing defective parts of wire networks in multilayer substrates, as required to detect defects in μm order resolution.
In the process of high-precision analysis, the individual propagation velocity of electrical pulse waves was derived in each small section on a signal line that includes a defect wire over the multiple layers and vias, by solving of a set of system of equations from a matrix of time and distance of plural reference lines and refection pulse wave results on these lines.
This was successful in specifying an open defect location on a line within a decades μm order period with a non-destructive method by high accurate TDR analysis using the individual derived propagation velocity factor of each section.
With the highly accurate defect detection method mentioned in this study, a more effective process of nano-meter level defect analysis for X-Ray inspection and destructive inspection as next steps can be estimated.
The propagation velocity analysis for each section examined in this paper is not only for identifying defective locations in the wiring in substrate, also for isolation via cracks or branches in wiring circuits over the layers, interposers, these connect soldering cracks on bumps, open/short defects of bonding parts, and defect points in parts of SiP (System in Package) devices.
In addition, defects of cracks were discovered with partial connections and not fully-open defects, by detecting small time domain waveform difference with slight impedance unmatching.

The propagation speed analysis for each section examined in this study can be applied not only to the identification of defective parts, also to the analysis of the impedance matching of each part and the propagation velocity in each part in high-speed signal propagation wiring design.