Introducing Functional Via Structures to Low Temperature Cofired Ceramics: How to Optimize Reliably and Efficiently

Abstract

Low temperature cofired ceramics (LTCCs) refer to a mature technology with low-loss dielectric materials, high quality conductors, and high dimensional accuracy. This class of ceramics-based substrates is a popular choice for integration of a variety of electronics with active and passive components in both single- and multilayered environments. Vertical interconnect accesses (vias) are widely used in LTCC and elsewhere for signal routing as well as power and ground supply within the stack-up. Since vias represent discontinuities in the signal path, they introduce parasitic elements that inevitably degrade the electrical performance. This work intends to delineate two distinct, straightforward, and efficient ways to estimate as well as control via impedance and phase delay. The usability of vias in LTCC is extended through the concept of functional via structures, which is based on the generalization of vias as quasi-coaxial lines that behave similarly to real transmission lines. The advantage of the proposed concept is highlighted by deploying vias for three-dimensional (3-D) integration of power dividers, and improving the signal integrity (SI) and power integrity (PI) of via arrays in LTCC multilayered substrates.