1. The spacing between patches
The spacing between SMD 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 and tinning.
The distance recommendations are as follows
Device distance requirements between patches:
Same kind of devices: ≥0.3mm
Dissimilar devices: ≥0.13*h+0.3mm (h is the maximum height difference of neighboring components)
The distance 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.
2. The distance between the in-line device and the patch
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.
3. For the placement of IC decoupling capacitors
A decoupling capacitor 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, a decoupling capacitor must be placed on each port.
4. Pay attention to the placement direction and distance of the components on the edge of the PCB board.
Since the PCB is generally made of jigsaw, 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 on the left side of the figure above, the different force directions of the two pads of the patch may cause the component and the welding to be split. Disc off)
The second is that components cannot be arranged within a certain distance (to prevent damage to components when the board is cut)
5. Pay attention to situations where adjacent pads need to be connected
If adjacent pads need to be connected, first confirm that the connection is made outside to prevent bridging caused by the connection, and pay attention to the width of the copper wire at this time.
6. If the pad falls in a normal area, heat dissipation needs to be considered
If the pad falls on the pavement area, the right way should be used to connect the pad and pavement. Also, determine whether to connect 1 line or 4 lines 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 by the copper laid, which makes the welding impossible.
7. If the lead is smaller than the plug-in pad, a teardrop is required
If the wire is smaller than the pad of the in-line device, you need to add teardrops as shown on the right side of the figure.
Adding teardrops has the following benefits:
(1) Avoid the sudden decrease of the signal line width and cause reflection, which can make the connection between the trace and the component pad tend to be smooth and transitional.
(2) The problem that the connection between the pad and the trace is easily broken due to impact is solved.
(3) The setting of teardrops can also make the PCB circuit board look more beautiful.