1. Our country is in a favorable situation with economic construction as the center and reform and opening up. The annual growth rate of the electronic industry will exceed 20%. The printed circuit board industry depends on the entire electronics industry and will rise with the trend, and the growth rate will exceed 20%. The technological revolution and industrial structural changes in the world’s electronics industry are bringing new opportunities and challenges to the development of printed circuits. With the development of miniaturization, digitization, high frequency, and multi-functionalization of electronic equipment, printed circuits, as the metal wires in the electrical interconnections of electronic equipment, are not only a question of whether current flows or not but also serve as signal transmission lines, affecting circuit performance. Therefore, for the electrical test of PCBs used for the transmission of high-frequency signals and high-speed digital signals, it is necessary to measure whether the circuit continuity and short-circuit meet the requirements, as well as whether the characteristic impedance value is within the specified qualified range. Only when these two criteria are met can the circuit board be deemed acceptable.
2. The circuit performance provided by the printed circuit board must be capable of preventing reflections during signal transmission, maintaining signal integrity, reducing transmission loss, and facilitating impedance matching to ensure a complete, reliable, accurate, interference-free, and noise-free transmission signal. This article discusses the characteristic impedance control of the surface microstrip structure multilayer board commonly used in practice.
3. **Surface Microstrip Line and Characteristic Impedance**
4. The characteristic impedance of the surface microstrip line is relatively high and is widely used in practice. Its outer layer is the signal line surface that controls the impedance, separated from the adjacent reference plane by insulating materials. The calculation of the characteristic impedance employs the following formulas:
a. **Microstrip Z** = (frac{87}{{sqrt{Er+1.41}}}) (lnleft[frac{5.98H}{{0.8W+T}}right]) where (W) is the line width, (T) is the copper thickness of the trace, (H) is the trace-to-reference-plane distance, and (Er) is the dielectric constant of the PCB material. This formula is applicable when (0.1
It can be observed from these formulas that the primary factors influencing the characteristic impedance are (1) dielectric constant (Er), (2) dielectric thickness (H), (3) wire width (W), and (4) wire copper thickness (T).
5. Therefore, the characteristic impedance and the substrate material (i.e., the copper clad board) are closely related, emphasizing the critical importance of substrate material selection in PCB design.
2. The circuit performance provided by the printed circuit board must be capable of preventing reflections during signal transmission, maintaining signal integrity, reducing transmission loss, and facilitating impedance matching to ensure a complete, reliable, accurate, interference-free, and noise-free transmission signal. This article discusses the characteristic impedance control of the surface microstrip structure multilayer board commonly used in practice.
3. **Surface Microstrip Line and Characteristic Impedance**
4. The characteristic impedance of the surface microstrip line is relatively high and is widely used in practice. Its outer layer is the signal line surface that controls the impedance, separated from the adjacent reference plane by insulating materials. The calculation of the characteristic impedance employs the following formulas:
a. **Microstrip Z** = (frac{87}{{sqrt{Er+1.41}}}) (lnleft[frac{5.98H}{{0.8W+T}}right]) where (W) is the line width, (T) is the copper thickness of the trace, (H) is the trace-to-reference-plane distance, and (Er) is the dielectric constant of the PCB material. This formula is applicable when (0.1
It can be observed from these formulas that the primary factors influencing the characteristic impedance are (1) dielectric constant (Er), (2) dielectric thickness (H), (3) wire width (W), and (4) wire copper thickness (T).
5. Therefore, the characteristic impedance and the substrate material (i.e., the copper clad board) are closely related, emphasizing the critical importance of substrate material selection in PCB design.
