Summary of matters needing attention in circuit board welding

1. After getting the PCB bare board, the appearance inspection should be carried out first to see whether there are problems such as short circuit and circuit break, and then get familiar with the schematic diagram of the development board, and compare the schematic diagram with the PCB screen printing layer to avoid inconsistency between the schematic diagram and PCB.

2. After the materials needed for PCB welding are ready, the components should be classified, and all components can be divided into several categories according to the size, so as to facilitate subsequent welding.A complete material list needs to be printed.In the welding process, if one item is finished, the corresponding option will be crossed out with a pen, so as to facilitate the follow-up welding operation.

3.Before welding, anti-static measures such as wearing electrostatic ring should be taken to avoid the harm of electrostatic to the components.After all necessary equipment is ready for welding, the soldering tip should be clean and tidy.It is recommended to use the flat-angle soldering iron for the first welding, which can better contact the pad for welding such as type 0603 packaging components.Of course, this is not a problem for the master.

4. When selecting components for welding, the components shall be welded in the order from low to high and from small to large.In order to avoid welding larger components to smaller components welding inconvenience.Preferred to weld IC chips.

5. Ensure the correct placement direction of IC chips before welding.For the chip screen layer, generally rectangular pad represents the starting pin.When welding, a pin of the chip should be fixed first. After fine-tuning the position of components, the diagonal pin of the chip should be fixed so that components are connected to the correct position before welding.

6. There are no positive and negative diodes in the chip ceramic capacitor and voltage regulator circuit, while the light-emitting diode, tantalum capacitor and electrolytic capacitor need to distinguish between positive and negative electrodes.For capacitor and diode components, the one end with a prominent mark should be negative.In the package of patch LED, the direction along the lamp is positive – negative.For silk-screen marking as diode circuit diagram packaging components, a vertical line should be placed at one end of the diode negative extreme.

7. For crystal oscillator, the passive crystal oscillator generally has only two pins, and there are no positive or negative points.Active crystal oscillator usually has four pins. Please pay attention to the definition of each pin to avoid welding errors.

8. For the welding of plug-in components, such as related components of power module, the pin of the device can be modified before welding.After the components are placed and fixed, generally melt the soldering tin through a soldering iron on the back and integrate it into the front.Do not put too much solder, but first make the components stable.

9. During the welding process, PCB design problems found, such as installation interference, incorrect pad size design, components packaging errors, etc. shall be recorded in time for subsequent improvement.

10. After completion of welding, magnifying glass should be used to check the welding spot to check whether there is false welding and short circuit, etc.

11. The circuit board welding work is completed, should use alcohol and other cleaning agents on the surface of the circuit board cleaning, prevent the circuit board surface adhesion of iron to make the circuit short circuit, but also can make the circuit board more clean and beautiful.

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