The following points must be achieved when soldering with a soldering iron:
1. The welding surface must be kept clean
Even for weldments with good weldability, harmful oxide films, oil stains, etc. may form on the surface of the weldment due to long-term storage and contamination. So, the surface must be cleaned before welding, otherwise it is difficult to ensure quality.
2. During welding, the temperature and time should be appropriate, and the heating should be uniform
When welding, heat the solder and the metal to be welded to the welding temperature, allowing the melted solder to wet and diffuse on the surface of the metal to form a metal compound. Therefore, to ensure the firmness of the solder joints, it is necessary to have an appropriate welding temperature.
At a sufficiently high temperature, the solder can fully wet and diffuse to form an alloy layer. Excessive temperature is not conducive to welding. The welding time has a significant impact on the wetting properties of the solder and welded components, as well as the formation of the bonding layer. Accurately mastering the welding time is the key to high-quality welding.
3. Welding points should have sufficient mechanical strength
In order to ensure that the welded parts do not fall off or loosen when subjected to vibration or impact, it is required that the welding points have sufficient mechanical strength. To ensure sufficient mechanical strength of the solder joints, it is generally possible to bend the lead terminals of the soldered components before soldering, but excessive solder accumulation should not be used, as this can easily cause virtual soldering and short circuits between solder joints.
4. Welding must be reliable to ensure conductivity
To ensure good conductivity of solder joints, it is necessary to prevent virtual soldering. Virtual welding refers to the situation where the solder does not form an alloy structure with the surface of the object being welded, but simply adheres to the surface of the metal being welded. When welding, if only a part forms an alloy while the rest does not, the weld can still pass current in the short term, and it is difficult to detect problems with instruments. But over time, the surface that has not formed an alloy will be oxidized, and a phenomenon of intermittent on-off will occur, which will inevitably cause quality problems with the product.
In short, good quality solder joints should be: bright and smooth solder joints; The solder layer is evenly thin and smooth, and the ratio to the size of the solder pad is appropriate. The outline of the joint is faintly visible; The solder is sufficient and spreads out in a skirt shape; No cracks, pinholes, or solder residue. The appearance of a typical solder joint is shown in Figure 8, where the height of the "skirt" shape is approximately 1 to 1.2 times the radius of the solder pad.
