Fabrication principle of High Frequency Printed Circuit Board
In high frequency PCB design, the power supply is designed as a layer, in most cases, it is much better than the bus design, so that the circuit can always follow the path with the least impedance. In addition, the power supply board has to provide a signal loop for all signals generated and received on the PCB, which can minimize the signal loop and thus reduce the noise, which is often ignored by the low frequency circuit designers.
In high-frequency PCB design, we should follow the following principles:
The unity of power and ground, stability.
Careful consideration of wiring and proper termination can eliminate reflection.
Carefully considered wiring and proper termination can reduce capacitive and perceptual crosstalk.
Noise suppression is needed to meet EMC requirements.
High frequency circuit board fabrication material requirements :
1.The dielectric loss (Df) must be small, which mainly affects the quality of signal transmission. The smaller the dielectric loss, the smaller the signal loss.
2.If water absorption is low, high water absorption will affect dielectric constant and dielectric loss.
3.The dielectric constant (DK) must be small and stable. Usually, the smaller the signal is, the better the signal transmission rate is inversely proportional to the square root of the dielectric constant of the material, and the high dielectric constant can easily cause the signal transmission delay.
4.The thermal expansion coefficient of copper foil is consistent with that of copper foil, because the inconsistency will cause the separation of copper foil during the change of cold and heat.
- Other heat resistance, chemical resistance, impact strength, peeling strength must also be good.
In general, high frequency can be defined as frequency above 1GHz. At present, the high frequency is the fluorine medium substrate, such as polytetrafluoroethylene (PTFE) usually called Tefluron.
High frequency circuit board machining attention point:
- 1.impedance control requirements are strict, relative line width control is very strict, general tolerance of about 2%.
- 2.because of the special plate, the adhesion of PTH is not high, so it is usually necessary to coarsening through hole and surface with plasma treatment equipment, so as to increase the adhesion of PTH hole copper and welding resistance ink.
3.Do not grind the plate before welding resistance, otherwise the adhesion will be very poor, can only use micro-corrosion solution and other coarsening.
- 4.plates are mostly PTFE materials, with ordinary milling cutter molding will have a lot of edges, special milling cutter.
- High frequency circuit board is a special circuit board with high electromagnetic frequency. Generally, high frequency can be defined as frequency above 1GHz. Its physical properties, precision and technical parameters are very high. It is often used in automobile anti-collision system, satellite system, radio system and other fields.