Wiring is a very important part of PCB design, which will directly affect the performance of PCB. During PCB design, different layout engineers have their own understanding of PCB layout, but all layout engineers are in agreement on how to improve wiring efficiency, which not only saves the client project development cycle, but also maximizes guaranteed quality and cost. The following describes the PCB design process and steps to improve wiring efficiency.

1, determine the number of layers PCB

Board dimensions and wiring layers need to be determined early in the design process. If the design requires the use of high-density ball grid array (BGA) components, the minimum number of wiring layers required to route these components must be considered. The number of wiring layers and the layering method directly affect the wiring and impedance of printed wiring. The size of the board helps determine the stack and line width to achieve the desired design.

2. Design rules and limitations

The automatic routing tool itself doesn’t know what to do. To accomplish routing tasks, routing tools need to work within the right rules and constraints. Different signal lines have different wiring requirements, and all special requirements of signal lines are classified, and different design classifications are different. Each signal class should have priority. The higher the priority is, the stricter the rule is. Rules concerning trace width, maximum number of through-holes, parallelism, interaction between signal lines, and layer limits have a great impact on the performance of routing tools. Careful consideration of design requirements is an important step in successful wiring.

3. Component layout

Optimize assembly processes and design manufacturability (DFM) rules to impose constraints on component layouts. If the assembly department allows components to move, the circuit can be optimized to automate wiring more easily. Rules and constraints defined affect layout design.

4. Fan out design

During the fan out design phase, for automatic routing tools that connect component pins, each pin of the surface mount device should have at least one through-hole so that the board can perform the inner layer when additional connections are required. Connectivity, in-line testing (ICT) and circuit reprocessing.

For the automatic routing tool to be most effective, the largest possible through-hole size and printed line must be used, with an interval of 50 mils preferred. Use a VIA type that maximizes the number of routing paths. When performing fan out designs, consider on-line testing of the circuit. Test fixtures can be expensive and are usually ordered when they are ready for full production. It’s too late to consider adding nodes to achieve 100% testability.

5, manual wiring and key signal processing

Although this article focuses on automatic routing, manual routing is an important process in present and future PCB design. Manual routing helps automatic routing tools complete routing work. Regardless of the number of critical signals, these signals can be routed first, manually, or used in combination with automatic routing tools. Critical signals must often be carefully designed to achieve the desired performance. It is relatively easy for engineering personnel to check signal wiring after wiring is completed. This process is relatively easy. After the inspection, the wire is fixed, and other signals are automatically routed.

6, automatic wiring

Wiring of critical signals requires consideration of controlling some electrical parameters during wiring, such as reducing distributed inductance and EMC, and wiring for other signals is similar. All EDA vendors provide methods to control these parameters. The quality of automatic wiring can be guaranteed to a certain extent after knowing the input parameters of automatic wiring tool and their influence on wiring.

7, the appearance of the board

Previous designs often focused on the visual effects of the board, but now it’s different. The circuit board designed automatically is not more beautiful than manual design, but it meets the requirements of electronic characteristics and ensures the integrity of the design.

For layout engineers, poor technique should not be judged by the number of layers and speed alone. Only when the number of components is equal to the signal speed and other conditions, the smaller the area, the fewer layers, the lower the cost. PCB board is well designed to ensure good performance and beauty. This is the master.