1. The interval between patches

The spacing between surface mount components is an issue that engineers need to pay attention to when laying out. If the spacing is too small, it will be difficult to print solder paste and prevent solder joints.

The interval proposal is as follows

Requirements for equipment spacing between patches:

Same type of equipment: ≥ 0.3mm

Heterogeneous equipment: ≥ 0.13 * h 0.3mm (h is the height difference between neighboring components)

The isolation requirement between components that can only be applied by craftsmanship: ≥ 1.5mm

The above claims are for reference only and can be based on the PCB process design specifications of each company

2. The interval between direct insertion equipment and surface mount

As shown in the figure above, the gap between the direct insertion resistor equipment and the surface mount should be maintained within 1-3mm, as it is difficult to process and the use of direct plugs is now rare.

3. Regarding the placement of decoupling capacitors for ICs

Decoupling capacitors need to be placed near the power ports of each IC, and their positions should be as close as possible to the power ports of the IC. When a chip has multiple power ports, decoupling capacitors should be placed at each port.

4. Pay attention to the placement direction and spacing requirements of the elemental equipment at the edge of the PCB board

Because PCBs are usually made using splicing boards, the equipment requirements near the edge meet two conditions.

Firstly, it is parallel to the cutting direction (to make the mechanical stress of the equipment uniform, for example, if the method shown on the left in the figure is used to place it, the different directions of force on the two solder pads of the patch may cause the components and solder pads to fall off when the panel needs to be disassembled)

The second is that equipment cannot be placed within a certain interval to prevent damage to the original equipment during board cutting

5. Attention should be paid to the situation where adjacent pads need to be connected

If adjacent pads need to be connected, first acknowledge the connection on the outside to prevent them from forming a bridge and pay attention to the width of the copper wire at this time.

6. If the solder pad falls in a general area, heat dissipation needs to be considered

If the solder pad falls in the through area, the method on the right should be adopted to connect the solder pad and the through area, and the connection between 1 wire and 4 wires should be determined based on the current magnitude.

If the method on the left is adopted, it may be difficult to weld or repair disassembled equipment, because the temperature is dispersed by the copper laid, resulting in poor welding performance.

7. If the lead is smaller than the plug-in pad, tears need to be added

If the wire is smaller than the solder pad of the direct insertion equipment, it is necessary to add a tear drop as shown on the right side of the picture.

Adding tears has the following benefits:

To prevent the sudden reduction of signal line width and the formation of reflection, it can make the connection between the wiring and the component pad tend to transition smoothly.

Solved the problem of simple breakage of the connection between the solder pad and the wire due to impact force.

Setting up tears can also make the PCB circuit board look more beautiful.

8. The width of the leads on both sides of the component pad should be the same

The width of the leads on both sides of the component pad should be common

9. Pay attention to keeping unused pin pads and grounding them

Be careful to keep unused pin pads and ground them correctly.

For example, in the case where two pins of a chip are not to be used in the above picture, but the chip's miscellaneous pins do exist, if the two pins are in a suspended state like the method on the right side of the picture, it is easy to cause interference. If the solder pads are added and grounded, shielding can prevent interference.

10. Do not drill through holes on solder pads

Be careful not to drill through holes on the solder pads, as it may cause solder leakage and virtual soldering.

11. Pay attention to the spacing between wires or equipment and the edge of the board

It should be noted that the leads or components should not be too close to the edge of the board, especially for single panels. Generally, single panels are mostly made of paper boards, which can easily break under stress. If there are connections or components placed at the edge, they will be affected.

12. It is necessary to consider keeping the ambient temperature of electrolytic capacitors away from heat sources

Firstly, it is necessary to consider whether the ambient temperature of the electrolytic capacitor meets the requirements. Secondly, the capacitor should be kept as far away from the heating area as possible to prevent the liquid electrolyte inside the electrolytic capacitor from drying out.

Article source: PCB manufacturerhttp://www.yonghongpcb.com/