Spacing between patches The spacing between patch components is a problem that engineers must pay attention to during layout. If the spacing is too small, it is very difficult to print solder paste and avoid soldering. The recommended distances are as follows: The distance requirements between the devices: Same device: ≥0.3mm Different devices: ≥0.13*h+0.3mm (h is the maximum height difference between neighboring components) The distance requirements between components that can only be manually patched: ≥1.5mm. The above suggestions are for reference only and can be in accordance with the PCB process design specifications of the respective companies
The distance between the in-line device and the patch is as shown in the figure above. There should be a sufficient distance between the in-line resistance device and the patch, and it is recommended to be between 1-3mm. Due to the troublesome processing, the use of straight plug-ins is rare now.
For the placement of IC decoupling capacitors, decoupling capacitors must be placed near the power port of each IC, and the location should be as close as possible to the power port of the IC. When a chip has multiple power ports, each port must Arrange decoupling capacitors.
Attention should be paid to the placement direction and distance of the components on the edge of the PCB. Since the PCB is generally made of jigsaw, the components 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 on the left side of the above figure, when the puzzle is to be split, the force direction of the two pads of the patch is different, which may cause the component and the welding The disk falls off) The second is that the components cannot be placed within a certain distance (to prevent damage to components when the board is cut)
If adjacent pads need to be connected, pay attention to if adjacent pads need to be connected, first confirm that the connection is made outside to prevent bridging caused by connecting together, and pay attention to the width of the copper wire at this time.
If the pad falls in the common area, heat dissipation needs to be considered. If the pad falls in the pavement area, the right way should be used to connect the pad and the pavement. Also, determine whether to connect 1 wire or 4 wires according to the current. If the method on the left is adopted, it is more difficult to weld or repair and disassemble the components, because the temperature is fully dispersed through the copper laid, which leads to the welding failure.
If the lead is smaller than the plug-in pad, you need to add teardrops. If the lead is smaller than the pad of the in-line device, you need to add teardrops. Adding teardrops has the following benefits: to avoid the sudden decrease of the signal line width and cause reflections, the connection between the trace and the component pad can be smoothly transitioned. The problem that the connection between the pad and the trace is easily broken by impact is solved. Setting teardrops can also make the PCB circuit board look more beautiful.
The width of the lead on both sides of the component pad should be the same. The width of the lead on both sides of the component pad should be the same.
Note that the pads of unused pins are reserved and grounded. Note that the pads of unused pins are reserved and grounded correctly. For example, in the picture above, two pins of a chip do not need to be used, but the physical pins of the chip exist. If the two pins on the right side of the picture above are in a floating state, it is easy to cause interference. If you add a pad and then ground the pad to shield it, interference can be avoided.
It is better not to punch the via hole on the pad. Note that the via hole is best not to be punched on the pad, which may easily cause leakage of solder.
Pay attention to the distance between wires or components and the edge of the board. Note that the leads or components should not be too close to the edge of the board, especially single-sided boards. Generally, single-sided boards are mostly paper boards, which are easy to break after stress. Put components will be affected.
12. It must be considered that the ambient temperature of the electrolytic capacitor is far away from the heat source. Firstly, whether the ambient temperature of the electrolytic capacitor meets the requirements should be considered. Second, the capacitor should be kept as far away from the heating area as possible to prevent the liquid electrolyte inside the electrolytic capacitor from being dried.