1. Consider the choice of components packaging

During the entire schematic drawing phase, component packaging and land patterns are required at the layout stage. The following gives some suggestions for consideration when selecting components based on component packages:

1) The package includes the electrical pad connections and mechanical dimensions (X, Y, and Z) of the component, that is, the outline of the component body and the pins that connect the PCB. When selecting components, consider any mounting or packaging restrictions that may exist on the top and bottom layers of the final PCB. Some components (such as polar capacitors) may have high limits and need to be considered during component selection. When you first start designing, you can draw a basic board outline and then place some large or location-critical components (such as connectors) that you plan to use. In this way, the virtual perspective of the board (without wiring) can be seen intuitively and quickly, and the relative positioning and component height of the board and components are relatively accurate. This will help ensure that the assembled components of the PCB fit properly into the outer packaging (plastics, chassis, chassis, etc.). The entire board can be viewed by calling the 3D preview mode from the Tools menu.

2) The pad pattern shows the actual pad or via shape of the soldered device on the PCB. These copper patterns on the PCB also contain some basic shape information. The size of the pads pattern needs to be correct to ensure proper soldering and to ensure proper mechanical and thermal integrity of the connected components. When designing the PCB layout, you need to consider how the board will be manufactured, or how the pads will be soldered if soldered by hand. Reflow soldering (flux melting in a controlled high temperature furnace) can handle a wide range of surface mount devices (SMD). Wave soldering is typically used to solder the reverse side of a board to secure via devices, but it can also handle some surface mount components placed on the back side of the PCB. Typically, when using this technique, the underlying surface mount devices must be aligned in a particular direction, and in order to accommodate this soldering method, the pads may need to be modified.

3) The choice of components can be changed throughout the design process. Early in the design process, it is determined which devices should use plated-through holes (PTH) and which should be surface-mount technology (SMT) to help the overall planning of the PCB. Factors to consider include device cost, availability, device area density, and power consumption. From a manufacturing perspective, surface mount devices are generally less expensive than through-hole devices and generally have higher availability. For small and medium-sized prototype projects, it is best to use larger surface mount devices or through-hole devices, which not only facilitates manual soldering, but also facilitates better connection pads and signals during troubleshooting and debugging.

4) If there is no ready-made package in the database, it is common to create a custom package in the tool.

2. Need Proper Ground Plane

Make sure the design has enough bypass capacitor and ground plane. When using an integrated circuit, make sure to use a suitable decoupling capacitor near the power supply end to ground (preferably the ground plane). The proper capacitance of the capacitor depends on the application, capacitance technology, and operating frequency. When bypass capacitors are placed between the power and ground pins and placed close to the correct IC pins, the circuit's electromagnetic compatibility and susceptibility can be optimized.

3. Allocate the virtual component package

Print a bill of materials (BOM) to check the virtual components. Virtual components are not packaged and will not be transferred to the layout phase. Create a bill of materials and look at all the virtual components in the design. The only entries should be the power and ground signals, as they are considered virtual components and are only processed in the schematic environment and are not passed to the layout design. Unless used for simulation purposes, components displayed in the virtual portion should be replaced with components with packages.

4. Make sure you have complete bill of materials data

Check the material list report for sufficient data. After creating a bill of material report, a careful review is performed to complete the incomplete device, supplier or manufacturer information in all component entries.

5. According to the component label sort

To help sort and check the bill of materials, make sure the component labels are numbered consecutively.

6. Examine redundant gates

In general, all redundant gates inputs should have signal connections to avoid hanging the input. Make sure that you check all redundant or missing gates and that all non-wired inputs are fully connected. In some cases, if the input is in a floating state, the entire system will not work properly. Take the dual op amps that are often used in design. If only one of the two op amp IC components uses one op amp, it is recommended to either use another op amp or ground the input of the unused op amp and place a suitable unit gain (or other gain). Feedback network to ensure that the entire component works properly.

In some cases, ICs with floating pins may not work properly within the specification. Usually, the IC can only meet the specifications when the IC device or other gates in the same device are not operating in saturation--the input or output is close to or in the component supply rail. Simulations typically do not capture this situation because the simulation model typically does not connect multiple parts of the IC together to model the floating connection effect.

Always keep in mind that sometimes preparing in the initial stage, especially when selecting components, this is very helpful for the production stage and the last time you use the PCB. Your selection of parts can (and frequently will) change through these programs, so be open and responsive to the locations that your design brings to you. 

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