Welding is one of the most important parts in the assembly process of electronic products by pcb manufacturers. If there is no corresponding welding process quality assurance, any well-designed electronic device is difficult to reach the design target. Therefore, during welding, the following must be done:
- The welding surface must be kept clean even if the weldability is good.
Due to long-term storage and contamination, the surface of the welding piece may produce harmful oxide film, oil stain and so on. Therefore, before the implementation of welding must clean the surface, otherwise it is difficult to ensure quality.
- The temperature and time of welding should be appropriate.
When welding is uniform, the solder and the welded metal are heated to the welding temperature, so that the molten solder soaks and diffuses on the surface of the welded metal and forms a metal compound. Therefore, to ensure that the solder joint is strong, must have the appropriate welding temperature. At high enough temperature, the solder can be wetted and diffused to form alloy layer. Too high a temperature is not good for welding. Welding time has a great influence on the wettability of solder, welding element and the formation of bonding layer. Correctly grasping welding time is the key to high quality welding.
- Solder joints must have sufficient mechanical strength.
In order to ensure that the welded parts do not fall off and become loose under vibration or shock, it is necessary to have sufficient mechanical strength of solder joints. In order to make the solder joint have sufficient mechanical strength, the method of bending the lead terminal of the welded component can be adopted generally, but it can not be accumulated with too much solder, which easily causes the virtual welding and the short circuit between the solder joint and the solder joint.
- Welding must be reliable and ensure electrical conductivity.
In order to make solder joint have good electrical conductivity, it is necessary to prevent virtual welding. Virtual welding means that there is no alloy structure between solder and solder surface, but simply attached to the surface of welded metal. In welding, if only a part of the alloy is formed and the rest is not, the solder joint can also pass through the current in a short period of time, and it is difficult to find a problem with the instrument. However, with the passage of time, the surface that does not form the alloy will be oxidized, which will lead to the phenomenon of time opening and breaking, which is bound to cause the quality problem of the product.
In short, the solder joints of good quality should be: bright and smooth solder joints; the solder layer is even and thin, and appropriate to the size of the pad, and the contour of the joint is vaguely visible; the solder is sufficient and spread out in the shape of a skirt; there are no cracks, pinholes, no flux residues.