How to Make a Printed Circuit Board
PCB fabrication capability becomes particularly important when dealing with high-frequency signals and weak signals which are two major difficulties in the field of microelectronics. So in this article, let’s discuss how to make a good PCB.
1.Clearly Design Goals
When receiving a new design task, clear the design goal is the first step. You need to make a standard board, a high-frequency board, small signal processing PCB, or a board with both high-frequency property and small signal processing?
If it is an ordinary PCB, you only need to achieve reasonable layout and wiring, and ensure that mechanical dimensions can be exactly the same as per requirements. When there is a signal line over 40MHz on the board, you have to give careful consideration to these signal lines, such as crosstalk between lines and other issues.
2.Understand Requirements for Wiring Layout
During the wiring layout process, some special components will have special requirements, for example, analog signal amplifiers used for LOTI and APH require a stable and small-ripple power.
3.Component Layout Considerations
The first factor to be considered is the electrical performance, put components with close connection as nearer as possible. Especially for some high-speed lines, the layout should make it as short as possible, and the power signal and small signal devices should be separated.
In the premise of achieving the circuit performance, you should consider the board’s mechanical size, the location of the socket, or if components’ placement is neat, beautiful, and easy to test, etc.
With the design conclusion of OTNI and star-shaped optical network, more boards with over 100MHz high-speed signal lines will need to be designed in the coming future.
Any long signal path on a printed circuit board can be considered as a transmission line. If the transmission delay of the line is much shorter than the signal rise time, then the main reflection produced during the signal rise will be submerged. Overshooting, kickback and ringing no longer occur. For most current MOS circuits, the trace length can be measured in meters with no signal distortion since the rise time is much greater than the transmission delay.
For integrated circuits, due to the faster edge speed, the length of the trace must be significantly shortened to preserve the signal integrity.