How to soldering SMD components by hand

In SMT processing, when repairing electronic products or making small batch samples, chip components often need to be soldered by hand. What should pay attention to when soldering SMT components by hand? What are the differences between soldering of SMD components and soldering of TH components?

(I). The difference between soldering TH components.

1. Soldering material: The solder wire is smaller. Generally, the solder wire with a diameter of 0.5~0.8mm should be used, a no-clean flux with less corrosiveness and no residue should be used.

2. Tools and equipment: Use smaller tweezers and electric soldering iron. The power of the electric soldering iron is not more than 20W, and the head of the electric soldering iron is tapered; if the requirements are higher, it is best to have a hot air workbench, SMT repair station and special tooling.

3. Operators are required to be proficient in soldering and testing skills and accumulated certain SMT work experience.

(II). Setting the temperature of the soldering iron

1. When soldering or removing components below 1206, like resistors, capacitors, inductors, chips below 5*5mm and less than 8 pins, the temperature of the electric soldering iron is set to 250~270℃.

2. except to the above components, the soldering temperature is set to 350~370℃.

(III). Precautions for soldering of SMD components by manual placement:

1. Before manual placement, you need to apply flux and solder paste to the soldering PADs of the printed circuit board.

2. Use manual placement tools to place SMT components. The tools for manual placement are: stainless steel tweezers, suction pen, 3~5x desktop magnifying glass or 5~20x stereo microscope, anti-static workbench, anti-static wrist strap.

3. Ensure that the pads are clean. There will usually be solder residual on the reworked PCB. Generally, electric soldering iron, suction wire and tin suction device are used. If possible, you can use a hot air gun to blow the solder residual, and then use a vacuum suction pump to suck the solder away.

Hand place component, also known as manual placement, is a method of assisting machine pick and place. To ensure that when the machine is not suitable for placement, the placement work can be carried out smoothly. The requirement of manual placement is higher than that of TH soldering, and requires the skilled operation of workers.