Before routing, you should make an analysis of the design and carefully set the tools and software, which will make the design meet standards more.
1. To determine the number of PCB layers
The size and number of routing layers of PCB should be determined in the preliminary stage of designing. The number of routing layers and ways of stack-up will directly influence routing and resistance of the printed wiring. Determining the size of the board will be beneficial to confirming the ways of stacking up so as to achieve the desired designing effect. At the current stage, the cost differences between different multi-layer boards. When designing, many circuit layers must be adopted and make the coating copper evenly spread.
2. The rules and limits of layout
To complete routing smoothly, routing tools need to operate in the correct rules and limited conditions. Each signal line should be classified in the order of priority based on specific requirements. The higher the level is; the stricter the rules are. The rules involve the width of printing wires, the maximum number of holes, depth of parallelism, interaction between the signal lines and limitations between different layers, which will have huge impact on the performance of routing tools.
3. Layout of the components:
In the process of optimizing assembling, the rule of DFM will limit the layout of the components. If the assembling department allows movement of components, circuits can be optimized to facilitate automatic routing. The rules and constraint conditions will also impact the design of distribution. Auto-routing tools can handle one signal at a time, however, the routing tools can handle routing like a designer through setting restraint conditions and layers of the routing signal.
For example, as for the layout of power lines:
1. In the layout of PCB, decoupling circuits of the power should be designed near the relevant circuits instead of the power part, or it will not only affect bypass, but also pulsating current will flow through the power circuits or ground circuits, leading to crosstalk.
2. As for direction of power inside the circuits, power supply should be from the final stage to the first stage and filter capacitor should be at the final stage.
3. As for some main current passages, if the current needs to be disconnected or measured in the process of adjusting or testing, there should be current gap in the printing wires in the layout.
Besides, regulated power supply should be installed separately on the printing boards. When power and circuits share the same printing boards, it should be avoided that regulated power supply and circuit components are mixed or power and circuits share the same ground wires, because this kind of routing will not only generate disturbance, also also makes it difficult to disconnect the load in maintenance. At that time, there is no other option but to cut part of the printing wires, which will damage the printing board.
But for the current stage, PCB Manufacturer surface treatment process hasn’t changed much and manufacturers seem to have a long way to go in pursuing the change, but it should be noted that a slow change in the long run will surely lead to tremendous changes. Under the circumstances of louder voice for environmental protection, PCB surface treatment technique will surely make great changes in the future.
The basic purpose of surface treatment is to ensure good weldability and electric performance. As copper tends to exists in the form of oxidizing materials in the nature, which is difficult to maintain in the state of the original copper, so copper needs special treatment. In the following assembling process, strong scaling powder needs to be used to remove the copper oxidizing material. Strong scaling powder is difficult to remove itself, therefore, it is seldom adopted in the industry.
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