@misc{9238989,
  abstract     = {{Microvias are key enablers of next-generation high-speed and high-density
electronic products. However, their signal-integrity performance can be affected by
manufacturing-induced non-idealities, including tapered sidewalls caused by laser
drilling and positional staggering caused by fabrication tolerances. This thesis
investigates the impact of microvia vertical geometry and manufacturing-induced
staggering on interconnects performance in multilayer Printed Circuit Board
(PCB) structures.
Full-wave electromagnetic simulations are performed to compare conventional
polygonal cylindrical microvia models with more realistic conical microvia
models. For different transition lengths, the antipad size is first optimized
in the cylindrical model to define a matched baseline design. The cylindrical
and conical geometries are then compared using mixed-mode S-parameters,
Time-Domain Reflectometry (TDR), Maximum Available Transmission (MAT),
impedance, and isolation. In addition, manufacturing-induced microvia staggering
is investigated by considering both hole misalignment and layer misalignment.
Representative special cases are used to examine the effects of offset direction
for hole misalignment, and the combined effects of offset direction and fan-out
direction for layer misalignment. Monte Carlo simulations are then performed with
Gaussian-distributed misalignment offsets to evaluate the statistical robustness of
the transition.
The results show that longer and higher-frequency transitions are more
sensitive to the microvia vertical geometry. The conical model leads to noticeable
differences in return loss, mode conversion, TDR, impedance, and isolation
prediction. For manufacturing-induced staggering, the differential-mode reflection
and transmission remain relatively stable in both the representative special
cases and the Monte Carlo simulations, whereas the differential-to-common-mode
conversion is more sensitive to geometrical asymmetry and exhibits a wider
statistical spread under Gaussian-distributed misalignment offsets.
Overall, this work provides useful guidance for microvia modeling,
manufacturing-tolerance evaluation, and robust Signal Integrity (SI) design in
high-speed High-Density Interconnect (HDI) PCB applications.
Keywords: Stacked microvia, differential interconnects, vertical microvia
geometry, conical microvia, staggering, hole misalignment, layer misalignment,
Monte Carlo analysis, SI.}},
  author       = {{Wang, Yimin}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Evaluating the Effects of Microvia Vertical Geometry and Staggering on Signal Integrity}},
  year         = {{2026}},
}