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 (such as polar capacitors) may have height headroom restrictions, which need to be considered in the component selection process. At the beginning of the design, you can draw a basic outline shape of the circuit board, and then put some large or position-critical components (such as connectors) that you plan to use. In this way, the virtual perspective view of the circuit board (without wiring) can be seen intuitively and quickly, and the relative positioning and component height of the circuit board and components are given relatively accurately. This will help to ensure that the components of PCB can be properly put into the outer packaging (plastic products, chassis, machine frame, etc.) after assembly. You can browse the whole circuit board by calling 3D preview mode from the tools menu. The pad pattern shows the actual pad or via shape of the soldered 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 the correct mechanical and thermal integrity of the connected components. When designing PCB layout, it is necessary to consider how the circuit board will be manufactured, or how the pads will be soldered if it is 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 generally used to solder the back of the circuit board to fix the through-hole devices, but it can also handle some surface mount components placed on the back of the PCB. Usually, when this technology is adopted, the bottom surface mount devices must be arranged in a specific direction, and in order to adapt to this welding method, the pads may need to be modified.
