1. Consider the choice of component packaging
In the entire principle diagram drawing stage, component packaging and pads pattern decisions that need to be made in the layout stage should be considered.
The encapsulation includes the electrical pile connection and mechanical size (X, Y, and Z) of the component, that is, the shape of the component body and the pins connected to the PCB. When selecting components, you need to consider any installation or packaging restrictions that may exist in the top and bottom layers of the final PCB.
Some components (if there are polar capacitors) may have a high degree of cleanliness and need to be considered during the selection of components. At the beginning of the design, you can first draw a basic circuit board's outer frame shape, and then place some large or position key components (such as connectors) planned to use.
In this way, you can intuitively and quickly see the virtual perspective view of the circuit board (without wiring), and give the relative positioning and component height of the relatively accurate circuit boards and components. This will help to ensure that the PCB can be placed in the outer packaging (plastic products, chassis, chart frames, etc.) after assembly. Call the three -dimensional preview mode from the tool menu to browse the entire circuit board.
The pad pattern shows the actual pad or perforated shape of the welding device on the PCB. These copper patterns on PCB also contain some basic shape information. The size of the pad pattern needs to be correct to ensure the correct welding and ensure the correct mechanical and thermal integrity of the components. When designing the PCB landscape, you need to consider how the circuit board will be manufactured or manually welded.
Retro -flow welding (welded in controlling high -temperature furnaces) can handle extensive types of table stickers (SMDs). Summit welding is generally used to weld the opposite of the circuit board to fix the pores, but it can also be processed on some table stickers placed on the back of the PCB. When using this technology, the underlying table sticker must be arranged in a specific direction, and in order to adapt to this welding method, the pad may need to be modified.
The selection of components can be changed throughout the design process. In the early days of the design process, determine which devices should be used with electroplating holes (PTH) and which should be used for PCB. Factors that need to be considered are device cost, available, density and power consumption of the device area, and so on. From the perspective of manufacturing, table stickers are usually cheaper than pores and general availability. For small and medium -sized prototype projects, it is best to choose larger table stickers or through -hole devices, which is not only convenient for manual welding, but also helps to better connect pads and signals during errors and debugging.
If there is no ready -made packaging in the database, customized packaging is generally created in the tool.
2. Use a good grounding method
Make sure the design has enough bypass capacitors and horizon. When using an integrated circuit, make sure to use the appropriate decoupled capacitor near the position near the power supply to the ground (preferably the ground surface). The appropriate capacity of capacitance depends on specific applications, capacitance technology and operating frequency. When the bypass capacitors are placed between the power and ground pins, and close to the correct IC pin, the electromagnetic compatibility and sensibility of the circuit can be optimized.
3. Distribute virtual element packaging
Print a list of materials (BOM) to check virtual components. The virtual element is not related to the encapsulation and will not be transmitted to the layout stage. Create a list of materials and check all the virtual components in the design. The only entry should be a power supply and ground signal, because they are considered virtual elements, and they are only specifically processed in the environment of the principles and will not be transmitted to the layout design. Unless it is used for simulation purposes, the elements displayed in the virtual part should be replaced with packaging components.
4. Make sure you have a complete material list data
Check whether there are sufficient data in the list of materials. After creating a list of material lists, carefully check it, and complete the incomplete devices, suppliers or manufacturers in all component entries.
5. Sort according to the component labeling
In order to help the sorting and viewing of the material list, ensure that the component label is continuously numbered.
6. Check the excess door circuit
Generally speaking, all the inputs of all excess doors should have a signal connection to avoid the input end hanging. Make sure you check all the excess or omitted door circuits, and all the input terminals that have no connection are completely connected. In some cases, if the input terminal is in a suspended state, the entire system cannot work correctly. Take the dual transport often used in the design. If only one op amp is used in the double -way op amp component, it is recommended to use the other op amp to be used, or the input end of the unwanted op amp is connected, and a suitable unit gain (or other gains (or other gains or other gains is distributed ) Feedback the network to ensure that the entire component can work normally.
In some cases, ICs with suspended pins may not work normally within the indicator range. Generally, only when the IC device or other doors in the same device do not work in the saturated state input or output near or at the component power rail, this IC can meet the index requirements. Simulation usually cannot capture this situation, because the simulation model generally does not connect multiple parts of the IC to the modeling suspension connection effect.
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