Reasons for poor welding quality
The requirements of manual welding for solder joints are: ① good electrical connection performance; ② certain mechanical strength; ③ smooth and round.
The common reasons for poor soldering quality are: ①The amount of solder used is too much, and the tin accumulation of the solder joint is formed; the solder is too little, and the solder joint is not enough to wrap. ② cold welding. When soldering, the temperature of the soldering iron is too low or the heating time is insufficient, the solder is not completely melted, infiltrated, the surface of the solder is not bright (not smooth), and there are small cracks (like bean curd residue!). ③Soldering with rosin, a layer of rosin is mixed between the solder and the components or the printed board, resulting in poor electrical connection. If the rosin with insufficient heating is mixed, there will be a layer of yellow-brown rosin film under the solder joint; if the heating temperature is too high, there will be a black film of carbonized rosin under the solder joint. In the case of insufficiently heated rosin film, soldering iron can be used for repair welding. For those that have formed a black film, it is necessary to “eat” the solder, clean the surface of the soldered component or the printed board, and re-solder. ④ Solder bridge. Refers to the excessive amount of solder, resulting in a short circuit between the solder joints of components. This is especially important when soldering ultra-small components and small printed circuit boards. ⑤ Excessive flux, a lot of rosin residue around the solder joints. When a small amount of rosin remains, you can gently heat it with an electric soldering iron to evaporate the rosin, or use a cotton ball dipped in absolute alcohol to wipe off excess rosin or flux. ⑥ The solder on the surface of the solder joint forms a sharp protrusion. This may be due to insufficient heating temperature or too little flux, and the improper angle when the soldering iron leaves the solder joint.
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