In general, high frequency can be defined as a frequency above 1GHz; high frequency circuit boards have much higher requirements on materials and process production than ordinary ones. So, how are high frequency PCB circuit boards made? Below I will share with you:
First of all, what are the concerns in high frequency circuit board design?
In high-frequency circuit design, the power supply is designed in the form of layers, so that the loop can always follow the path of least impedance. In addition, the power board must provide a signal loop for all signals generated and received on the PCB, which can minimize the signal loop and thus reduce the noise.
We should follow the following principles:
- 1. The power supply and the ground are unified and stable.
- 2. Careful wiring and proper termination can eliminate reflections.
- 3. Careful wiring and proper termination can reduce capacitive and inductive crosstalk.
- 4. Noise suppression is required to meet EMC requirements.
Secondly, what are the requirements for high-frequency circuit board production materials?
- 1. The dielectric loss must be small, otherwise it will affect the quality of signal transmission; the smaller the dielectric loss, the smaller the signal loss.
- 2. Low water absorption, high water absorption will affect the dielectric constant and dielectric loss when wet.
- 3. The dielectric constant must be small and stable, and high dielectric constant can easily cause signal transmission delay.
- 4. The thermal expansion coefficient of the copper foil should be as consistent as possible, otherwise the copper foil will be separated during the change of cold and heat.
- 5. Other heat resistance, chemical resistance, impact strength, peel strength, etc. must be good.
At present, the most commonly used high-frequency sheet is a fluoropolymer substrate, such as polytetrafluoroethylene (PTFE), which is usually called Teflon.
Finally, the main points to pay attention to in the processing of high-frequency circuit boards:
- 1. The impedance control requirements are relatively strict, and the relative line width control is very strict, and the general tolerance is about 2%.
- 2. Due to the special plate, the adhesion of PTH copper sinking is not high. Usually, it is necessary to roughen the vias and the surface with the help of plasma treatment equipment to increase the adhesion of PTH hole copper and solder resist ink.
- 3. Do not grind the board before making the solder mask, otherwise the adhesion will be very poor, and it can only be roughened with micro-erosion potion.
- 4. Most of the plates are polytetrafluoroethylene materials, and there will be many burrs when forming with ordinary milling cutters, and special milling cutters are required.
- 5. Special circuit boards with high electromagnetic frequency are used, and the frequency is above 1GHz.
The above is the interpretation of the relevant knowledge of "how high-frequency PCB circuit boards are made". I believe you should have a more in-depth understanding of high-frequency circuit boards now, right?