On dielectric constant and loss tangent of dielectric material for circuit boards
– Difference in measurement methods and definitions and attentions need to be paid in applying them to circuit design –
Aug-2021
1 Introduction
Current high-speed communication systems, whether wireless or wired, demand every electric components to realize high performances in wider bandwidth at higher higher frequency band in order to achieve still higher communication capacity and quality. Accurate dielectric constant (Dk) and loss tangent (Df) from DC to millimeter wave band over 110 GHz now become the critical information for circuit designers. In addition, by improving the estimation accuracy of device characteristics at the design stage, the development cycle can be shortened, which is effective in reducing costs. Therefore, the exact Dk and Df values are also quite important information for the designers in this regard as well.
Under these circumstances, almost all companies supplying laminate materials used in printed circuit boards (PCBs) and integrated circuit packages provide their Dks and Dfs in various frequency bands. However, Dks and Dfs, and their effective values of circuits, are extracted according to different measurement methods, and they have different definitions. This situation sometimes can cause problems for circuit designers.
Why are two set of Dk and Df need for?
(White Paper PDF)
Sep-2020
We are on providing two sets of permittivity (Dk) and loss tangent (Df) for our principal high-frequency board material for designer’s conveniences. One is measured by a balanced-type circular disk resonator (BCDR) method, and the other is extracted by a transmission line method (TLM) using microstrip lines (MSLs) with characteristic impedance of 50 ohm. Why is the two data sets needed? As a serious designer has already aware, the two sets of data are generally not coincide and generally show different frequency dependencies as shown in the figure, therefore, he or she should use the two set of data properly according to the situation.
Electric fields in a BCDR is widely spreading out in the resonator and polarizing strictly perpendicular to the circuit board under test. Accordingly extracted Dks and Dfs by the method are quite accurate for the electric fields with such field distribution and polarization, and they can be considered as volume averaged values of materials consisting of the board. Designers can determine from this data whether the board material is adequate for their purpose at coarse design. However, the data isn’t suitable for detailed design. As is well known that electric fields propagating through all planar transmission lines are generally not perpendicular to a board and localized near the lines.
Panasonic RF simulation technology for PCB materials enables the next generation of
high-speed communications(White Paper PDF)
Mar-2020
A precise knowledge of printed circuit board (PCB) dielectric constant (Dk) and loss tangent (Df) values in the 100 GHz range is essential information for circuit designers developing the next generation of wireless communication systems including 5G, automotive radar sensors, future high-speed data transmission systems. As a premier supplier of high-performance circuit board laminates, it is valuable for Panasonic to provide accurate Dk and Df data at high frequency bands to enable customer designs. In this vein, Panasonic is continually developing equipment and processes for evaluating high speed transmission properties and determining PCB Dk and Df values at frequencies up to 110 GHz.
Determining frequency-based insertion loss and time-delay behaviors for transmission lines, especially those with full-band and single-sweep from DC to 110 GHz, are some of the most basic criteria in determining if a PCBs design is suitable for the target application. This behavior is especially relevant for high speed data transmission applications, e.g., PAM4, because the time-domain propagation properties,