As the PCB size becomes smaller and the device density is higher and higher, although the current EDA tools are very powerful, the difficulty of PCB design is not small. As the most time-consuming link in the PCB design process, what are the efficient PCB layout skills?
1. Determine the number of layers of the PCB
Board size and wiring layers need to be determined early in the design. If the design calls for the use of high-density ball grid array (BGA) components, the minimum number of routing layers required to route these devices must be considered.
2. Design rules and restrictions
To accomplish the routing task, the routing tool needs to work within the correct rules and constraints. Different signal lines have different wiring requirements, and all signal lines with special requirements must be classified, and different design classifications are also different. Rules related to trace width, maximum number of vias, parallelism, interaction between signal lines, and layer constraints have a great impact on the performance of routing tools.
3. Wiring in order
In order to achieve the best wiring of printed boards, the wiring order should be determined according to the sensitivity of various signal lines to crosstalk and the requirements of wire transmission delay. Generally, wiring should be done in the following order:
a) Analog small signal lines;
b) Signal lines that are particularly sensitive to crosstalk;
c) System clock signal line;
d) Signal lines with high requirements for wire transmission delay;
e) general signal lines;
f) Static potential lines or other auxiliary lines.
4. Fan-out design
In the fan-out design phase, to allow the auto-routing tool to connect the component pins, each pin of the surface mount device should have at least one via, so that the board can be routed to the inner layer when more connections are required. Connectivity, In-Circuit Test (ICT) and Circuit Reprocessing.
5. Manual wiring and key signal processing
No matter how powerful the EDA tools are, manual routing is and will always be an important process in PCB design. Use manual routing to help the automatic routing tool to complete the routing work.
6. Automatic routing
The wiring of key signals needs to consider controlling some electrical parameters during wiring. After understanding the input parameters of the automatic wiring tool and the impact of the input parameters on wiring, the quality of automatic wiring can be guaranteed to a certain extent.
