The PCB is designed to be smaller,
faster and cheaper.As the interconnection point is the weakest link in the
circuit chain, in RF design, the electromagnetic property of the
interconnection point is the main problem faced by engineering design. It is
necessary to investigate each interconnection point and solve the existing
problems.The interconnection of the circuit board system includes three types
of interconnection, namely chip to circuit board, interconnection within PCB
board and signal input/output between PCB and external device.This paper mainly
introduces the practical skills of high frequency PCB design for interconnection in PCB board, and I believe this paper
will bring convenience to future PCB design.The interconnection between chip
and PCB in PCB design is important for design. However, the main problem of
interconnection between chip and PCB is that too high interconnection density
will lead to the basic structure of PCB material becoming the factor limiting
the growth of interconnection density.This article shares practical tips for
designing high frequency PCB.
For high frequency applications, PCB interconnection for high
frequency PCB design techniques are:
1, the transmission line to the corner a 45 °
Angle, in order to reduce return loss;
2. High performance insulation board with
strict control of insulation constant values should be adopted.This method can
effectively manage the electromagnetic field between the insulation material
and the adjacent wiring.
3. Perfect PCB design specifications for
high-precision etching.Consider setting the total line width error to +/-0.0007
inches, managing undercuts and cross-sections of wiring shapes, and specifying
lining plating conditions.The overall management of the wiring geometry and
coating surface is very important for solving the skin effect problems related
to microwave frequency and realizing these specifications.
4. There is tap inductance for protruding
leads, and the components with leads should be avoided.In high frequency
environments, it is best to use surface mount components.
5. For the signal via hole, it is necessary
to avoid using the process of via hole processing (PTH) on the sensitive
plate.Because this process will lead to lead inductance through the hole.A lead
inductance can affect 4 to 19 layers if a through hole on a 20 - layer plate is
used to connect 1 to 3 layers.
6. It should provide abundant ground.These
layers are connected by moulded holes to prevent 3 - dimensional
electromagnetic fields from affecting the circuit board.
7. Choose non-electrolytic nickel plating or
dip plating process instead of HASL electroplating.This electroplating provides
a better skin effect for high-frequency currents.In addition, this high
solderable coating requires less lead, helping to reduce environmental
pollution.
8. The resistance welding layer can prevent
the flow of solder paste.However, due to the uncertainty of thickness and the
uncertainty of insulation performance, the whole surface of the board is
covered with resistance welding material, which will lead to great changes in
electromagnetic energy in microstrip design.Solderdam is usually used as solder
barrier layer.
EAGLE DRIVER ELECTRONIC LIMITED。High frequency PCB,
specialized board manufacturer.（jackie@eagle-driver.com）
