source:Other information release time:2023-04-06 Hits: Popular:PCB Assembly company
Wiring is an extremely important part of the PCB design, which will directly affect the performance of the PCB board. During the PCB design process, the Layout engineer has its own understanding of Layout, but all Layout engineers are consistent in how to improve the wiring efficiency. Quality and cost. The following is the general design process and steps.
1. Determine the number of layers of PCB
The size of the circuit board and the number of wiring layers need to be determined in the early stage of the design. If the design requires the use of a high -density grid array (BGA) component, you must consider the minimum number of wiring layers required for the wiring of these devices. The number of wiring layers and the stack-up method directly affect the wiring and impedance of the printing line. The size of the board helps to determine the layers of layers and the width of the lines, and achieve the designed effect.
2. Design rules and restrictions
The automatic wiring tool itself does not know what to do. To complete the wiring task, the wiring tool needs to work under the correct rules and restrictions. Different signal cables have different wiring requirements. The signal lines of all special requirements should be classified, and different design classifications are different. Each signal class should have priority, the higher the priority, and the stricter the rules. The rules involve the width of the lines, the maximum number of perforated, parallelism, the interaction between the signal lines, and the restrictions of layers. These rules have a great impact on the performance of the wiring tool. Carefully considering the design requirements is an important step of successful wiring.
3. The layout of the component
In order to optimize the assembly process, the manufacturing design (DFM) rules will limit the component layout. If the assembly department allows the component to move, it can be appropriately optimized to the circuit and it is easier to automatically wiring. The defined rules and constraints will affect layout design.
4. Fan out of design
During the design stage of the fan, the automatic wiring tool should be connected to the component pins. Each pin of the surface installation device should have at least one perforated so that when more connections are needed, the circuit board can perform the inner layer in the inner layer. Connect, online test (ICT) and circuit re -processing.
In order to make the automatic wiring tool efficiency, it is necessary to use the maximum perforated size and printing line as much as possible. The interval is set to 50mil ideal. The most perforated type of the wiring trail should be adopted. When the fan is carried out, consider the online testing problem of the circuit. The test fixture may be expensive, and it is usually ordered when it is about to be put into full production. It is too late to consider adding a node to achieve 100%testability at this time.
5. Manual wiring and processing of key signals
Although this article mainly discusses the problem of automatic wiring, manual wiring is an important process for printing circuit board design now and in the future. Use manual wiring to help automatic wiring tools to complete the wiring work. Regardless of the number of key signals, first of all, you can carry these signals, manually wiring or combined with automatic wiring tools. Key signals usually must be designed with careful circuit design to achieve the expected performance. After the wiring is completed, the relevant engineers will check these signal wiring. This process is relatively easy. After passing the inspection, fix these cables, and then start automatic wiring on the remaining signals.
6. Automatic wiring
For the wiring of key signals, you need to control some electrical parameters during wiring, such as reducing distributed inductance and EMC, which are similar to other signals. All EDA manufacturers provide a method to control these parameters. After understanding the input parameters of the automatic wiring tool and the impact of the input parameter on the wiring, the quality of the automatic wiring can be guaranteed to a certain extent.
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