1. In high-frequency PCB design, use 45-degree angles for transmission line corners to reduce signal loss.
2. Employ high-performance insulation materials with strictly controlled dielectric constants for different layers in high-frequency PCB design. This approach helps effectively manage the electromagnetic fields between insulating materials and adjacent traces.
3. Ensure an abundance of ground layers in high-frequency PCB design. Utilize blind vias to interconnect these ground layers to prevent the influence of three-dimensional electromagnetic fields on the circuit board.
4. Be cautious of lead inductance in components with leads. It's advisable to avoid components with leads in high-frequency environments. Surface mount components are preferred for high-frequency designs.
5. Avoid using plated through-hole (PTH) technology for signal vias in sensitive areas of high-frequency PCB design. PTH technology can introduce lead inductance at the vias, affecting adjacent layers. For example, on a 20-layer board, a via connecting layers 1 to 3 could impact layers 4 to 19.
6. Develop precise specifications for high-precision etching in high-frequency PCB design. Consider specifying a total line width tolerance of +/- 0.0007 inches, managing undercut and cross-sectional profiles, and defining plating conditions for trace sidewalls. Managing the overall geometry and surface coating of traces is crucial to address skin effect issues related to microwave frequencies.
7. Choose non-electrolytic nickel or immersion gold processes instead of using HASL (Hot Air Solder Leveling) for surface plating in high-frequency PCB design. These plating surfaces provide better skin effect for high-frequency currents. Additionally, such plating requires fewer leads, contributing to reduced environmental pollution.
8. Solder mask layers prevent solder paste from flowing. However, covering the entire board surface with solder mask material can lead to significant variations in electromagnetic energy in microstrip designs due to uncertainties in thickness and insulation performance. Solder dams are generally used as solder mask layers.
If you're not familiar with these methods, you can seek advice from experienced design engineers who have worked on military microwave circuit board or RF circuit board design. You can also discuss your budget constraints with them. For instance, employing a copper-backed coplanar microstrip design might be more economical than a strip line design, and discussing this with experts can yield valuable suggestions. While exceptional engineers might not naturally consider cost concerns, their advice can still be highly valuable. It's crucial to cultivate younger engineers who lack experience in handling RF effects and train them for the long term.
