High-frequency PCB design in the chip and high-frequency PCB interconnection is important to the design, however, Chip and high-frequency PCB interconnection of the main problem is that the interconnection density is too high will lead to high-frequency PCB material basic structure to become a limiting interconnect density growth factor. This article has shared the practical skills of high-frequency PCB design. For high-frequency applications, high-frequency PCB board interconnect in the high-frequency PCB design techniques are:
1, transmission line corner to use 45° angle to reduce the return loss;
2, to use the dielectric constant value of the layer strictly controlled by the High-performance dielectric circuit board. This method is advantageous to the effective simulation calculation of the electromagnetic field between insulating material and adjacent wiring.
3, to specify high precision etching high-frequency PCB design specifications. High Frequency PCB It is considered that the total error of the line width is +/-0.0007 inches, the cutting (undercut) and cross section of the wiring shape is managed and the plating condition of the side wall of the wiring is specified. The overall management of the wiring (wire) geometry and coating surface is very important to solve the problem of skin effect related to microwave frequency and to realize these specifications.
4, protruding pin leads have tap inductance and parasitic effect, High Frequency PCB to avoid the use of lead components. High-frequency environment, it is best to use the surface Mount SMD components.
5, for the signal over the hole, to avoid the use of the sensitive plate on the process of processing (PTH), because the process will lead to the production of the lead inductance at the hole. If a pass hole on a 20-layer board is used to connect 1 to 3 layers, the lead inductance exists in 4 to 19 layers, with buried blind holes or back drills.
6, to provide a rich grounding layer. High Frequency PCB To use molded holes to connect these grounding layers to prevent the 3-D electromagnetic field from affecting the circuit board.
7, to choose non-electrolytic nickel plating or immersion gold plating process, do not use HASL method for electroplating. This electroplating surface provides a better skin effect for high-frequency currents. In addition, the high solder coating requires less lead, High Frequency PCB which helps to reduce environmental pollution.
8, solder resistance layer can prevent the flow of paste. However, due to the uncertainty of thickness and the unknown properties of dielectric constant, the entire surface of the plate will be covered with solder-resistance material, which can lead to the change of circuit performance in microstrip design. Welding Dam (Solderdam) is generally used as solder-resistance layer.
High frequency PCB is mainly a kind of special circuit board with high electromagnetic frequency, because of its physical index, precision and technical parameters and other indicators have a high demand, in the production need to pay strict attention to each production link indicators are in the normal range, High Frequency PCB is widely used in satellite systems, radio systems and automobile anti-collision systems and other fields.
So, high-frequency PCB has what wiring note?
First, in order to effectively manage the insulation materials and high-frequency PCB adjacent to the wiring between the electromagnetic field, should be the use of insulation value at the level of strict control of high-performance insulation high-frequency PCB, and in order to reduce the loss of circuit board transmission line Corner should also use 45 degrees.
Second, high-frequency PCB in the wiring process in order to highlight the presence of wire-tap inductance, should avoid the use of all lead components, High Frequency PCB and in the high-frequency environment should also use the surface mounting components, and for the signal through the hole in order to avoid the hole machining process caused by the lead inductance, should be prohibited on the sensitive plate using the hole processing technology.
Third, in order to prevent the three-dimensional electromagnetic field on the high-frequency PCB impact, should provide a rich street floor and the use of molded holes to connect these grounding layer together, at the same time in the electroplating operation should be the use of non-electric contact nickel plating or immersion alternative Hasl method, due to the plating surface of the high solder coating required less lead to help reduce environmental pollution.
Four, High Frequency PCB because of the high frequency PCB resistance welding layer due to the thickness and insulation performance uncertainty, in order to prevent the entire surface of the resistance welding material caused by its electromagnetic energy changes, should be used as far as possible to use the welding dam as a resistance welding layer electromagnetic field.