12 details that are easily overlooked in the PCB layout

The spacing between the chip components is a problem that engineers must pay attention to when laying out. If the pitch is too small, it is very difficult to solder paste printing and avoid soldering.

1, the distance is recommended as follows

Device distance requirements between patches:

Same kind of device: ≥0.3mm

Heterogeneous device: ≥0.13*h+0.3mm (h is the maximum height difference of surrounding neighbors)

Distance between components that can only be manually patched: ≥1.5mm.

The above recommendations are for reference only and can be based on the PCB design specifications of their respective companies.

2, the distance between the device and the patch

There should be a sufficient distance between the in-line resistor device and the patch. It is recommended to be between 1-3mm. Due to the troublesome processing, the use of straight plug-ins is now rare.

3. Place the decoupling capacitor of the 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, in the PCB board edge of the direction and distance of the components need to pay attention

Since the PCB is generally used for the PCB, the device near the edge needs to meet two conditions. The first is parallel to the cutting direction. (The mechanical stress of the device is uniform. For example, if it is placed in the way to the left of the above figure, the difference in the direction of the two pads of the patch may cause the element and the pad to fall off when the board is to be split. The second is that the device cannot be placed within a certain distance. (to prevent damage to components when the board is cut)

5, the need to pay attention to the need to connect adjacent pads

If adjacent pads need to be connected, first make sure to connect them outside to prevent bridging, and pay attention to the width of the copper wire at this time.

6. If the pad falls in the normal area, you need to consider heat dissipation.

If the pad falls in the paved area, the right side should be used to connect the pad to the paving, and depending on the current, it is determined whether to connect 1 line or 4 lines. If the method on the left is adopted, it is more difficult to weld or repair the components, because the temperature is dispersed by the copper of the paving, so that the soldering is not good.

7, the lead is smaller than the plug pad, you need to add teardrops

If the wire is smaller than the pad of the in-line device, you need to add the teardrop to the right side of the figure.

Adding teardrops has the following benefits:

1. Avoid the signal line width suddenly becoming smaller and causing reflection, which makes the connection between the trace and the component pad tend to be smooth transition.

2. Solved the problem that the connection between the pad and the trace is easily broken by the impact force.

3, set the teardrop can also make the PCB circuit board look more beautiful.

8, the width of the lead on both sides of the component pad should be consistent

9. Be careful to keep the pads of unused pins and ground them properly.

If two pins of a chip are not used, but the physical pin of the chip is present, it is easy to cause interference if the two pins are left floating. If the pad is added, the pad ground shield can avoid interference.

10, pay attention to the through hole is best not to hit the pad, it is easy to cause leakage tin solder joint.

11, pay attention to the distance between the wire or component and the edge of the board

Note that the lead wire or component cannot be too close to the edge of the board, especially the single panel. Generally, the single panel is mostly a paper board, which is easy to break after being stressed. If it is connected at the edge or the component is placed, it will be affected.

12, must consider the ambient temperature of the electrolytic capacitor away from the heat source

First, consider whether the ambient temperature of the electrolytic capacitor meets the requirements, and secondly, keep the capacitor as far as possible from the heat-generating area to prevent the liquid electrolyte inside the electrolytic capacitor from being dried.