This is relatively simple, and it goes without saying that everyone knows why. But you should also pay attention when soldering, for example, take a glance at the resistance value of the resistor to confirm that the position of the resistor and capacitor is correct.
A colleague before, soldered a resistor into a capacitor, or soldered a 1K into a 10K. When debugging, it either didn't work properly, or the machine was directly failed. If you do it all at once, you can save a lot of time.
2. Solder the IC in the QFN package first
Since the component pins of this package are on the back of the chip, the soldering iron cannot be directly contacted, so a hot air gun should be used for preheating soldering. Pay attention to setting the temperature and air volume of the air gun, generally around 300 ℃.
3. Soldering resistance and capacitance components
If several pins are tinned at the same time, the components cannot be completely attached to the PCB. During the process of moving the board, the board itself will be slightly deformed, which will cause some components to break. It's not easy to find the problem.
4. Solder the power chip first, and then solder other ICs
Many ICs need power supply. Only by ensuring the normal power supply can ensure that other chips are not burned.
5. Finally solder the MCU
Why solder the MCU last? Because its price is the most expensive, ranging from dozens to hundreds. Therefore, it is necessary to ensure that other components are soldered, and the power supply is normal before soldering the MCU.
Remarks: If you need to prepare at least two sets of PCB prototype, you can solder two pieces at the same time, which is more efficient than soldering them separately.
