Pcb12 circuit tips for layout

1. Spacing between patches
The spacing between chip components is a problem that engineers must pay attention to in layout. If the spacing is too small, it is very difficult to print solder paste and avoid soldering.
Suggested distances are as follows
Device distance requirements between patches:
Same device: ≥ 0.3mm.
Heterogeneous devices: ≥0.13*h+0.3mm(h is the maximum height difference of the neighboring elements)
Distance requirement between components that can only be pasted manually: ≥ 1.5mm. 。
The above suggestions are for reference only, and you can follow the PCB process design specifications of your respective companies.
2. Distance between the in-line device and the patch
As shown in the above figure, a sufficient distance should be kept between the in-line resistor device and the patch, and it is recommended that it should be between 1 and 3 mm. Because of the troublesome processing, there are few cases of using straight plug-ins now.
3. Placement of decoupling capacitors for IC
Decoupling capacitors should be placed near the power port of each IC, and the position should be as close as possible to the power port of the IC. When a chip has multiple power ports, decoupling capacitors should be placed at each port.
4. Attention should be paid to the placement direction and distance of components on the edge of PCB.
Because the PCB is usually made of patchwork, the devices near the edge need to meet two conditions.
The first is to be parallel to the cutting direction (to make the mechanical stress of the device uniform, for example, if the device is placed in the way shown on the left of the above figure, when the puzzle is to be split, the stress directions of the two pads of the patch are different, which may cause the component and the pad to fall off).
The second is that the components cannot be arranged within a certain distance (to prevent the components from being damaged when the board is cut).
5. Attention should be paid to the situation that adjacent pads need to be connected.
If the adjacent pads need to be connected, first make sure to connect them outside to prevent bridging caused by bunching, and pay attention to the width of the copper wire at this time.
6. If the pad falls in a common area, heat dissipation should be considered.
If the pad falls in the paved area, the right way should be adopted to connect the pad with the paved area. In addition, it is determined whether to connect one wire or four wires according to the current. If the left method is adopted, it is more difficult to weld or repair and disassemble components, because the temperature is completely dispersed by the paved copper, which leads to poor welding.
7. If the lead is smaller than the plug-in pad, you need to add tears.
If the wire is smaller than the pad of the in-line device, you need to add a tear drop in the way on the right of the above figure.
Adding tears has the following benefits:
1. Avoid the reflection caused by the sudden decrease of the signal line width, which can make the connection between the wiring and the component pad tend to be smoothly transitioned.
2. It solves the problem that the connection between the pad and the trace is easily broken by impact force.
3. Setting the tear drops can also make the PCB circuit board look more beautiful.
8. The width of leads on both sides of the component pad should be consistent.
The width of leads on both sides of the bonding pad should be consistent.
9. Pay attention to keep the pads of unused pins and ground them.
Pay attention to keep the pads of unused pins and properly ground them.
For example, in the above picture, two pins of a chip should not be used, but the physical pins of the chip exist. If the two pins are in a suspended state as shown on the right side of the above picture, it is easy to cause interference. If the pad is added and the pad is grounded, the interference can be avoided.
10. It is best not to hit the via on the pad.
Note that it is best not to hit the through hole on the pad, which may easily lead to solder leakage and virtual soldering.
11. Pay attention to the distance between wires or components and the board edge.
Pay attention to the fact that the leads or components can’t be too close to the edge of the board, especially the single panel. Generally, the single panel is mostly made of paper, which is easy to break after being stressed. If the wires or components are connected at the edge, it will be affected.
12. It must be considered that the environmental temperature of electrolytic capacitor is far away from the heat source.
First of all, it is necessary to consider whether the ambient temperature of the electrolytic capacitor meets the requirements. Secondly, it is necessary to keep the capacitor as far away from the heating area as possible to prevent the liquid electrolyte inside the electrolytic capacitor from drying out.