For the soldering industry, the melting point of solder wire
without lead must be increased by at least 20-45°C according to the difference in composition. In this way, the temperature setting of the soldering iron tip must also increase accordingly. As the temperature increases, the evaporation rate of the flux also increases, and the flux is the key factor that determines the metal activity (fluidity) after the solder wire is melted. Excessively high temperature will cause the flux to evaporate too fast, which will directly cause the lack of tin fluidity, and cause defects such as tin tip, tin bridge or wire drawing that seriously affect the soldering effect. For lead-containing solder wire, as long as the soldering iron tip is kept in the working temperature environment for too long, a layer of scorched oxide will form on the tip of the soldering iron tip. This phenomenon is more severe in the process of lead-free soldering, and the speed of occurrence is several times that of lead-based soldering, and the oxide produced by the interaction between the metal and flux in a high-temperature aerobic environment will seriously affect The normal amount of tin eaten at the front end of the soldering iron tip.
Leaded solder wires are divided into leaded solder wires with different grades, different prices and different effects according to their tin content. How should we distinguish and choose the quality of solder wires among so many kinds of solder wires?
Gloss color: This is directly related to the quality grade of solder wire and the amount of tin content. Gloss color not only affects the appearance but also affects the welding effect. Glossy and bright colors must have high tin content and good welding effect, otherwise the welding effect will be lacking, and even dull or whitish color will appear, which is not a normal shiny color.
Residue and smoke concentration: The flux component in the lead solder wire will leave residue and smoke together when it burns during soldering. When the solder wire is soldered, the thicker the smoke, the more residues there may be. The smoke will affect the physical and mental health of operating workers. Therefore, when choosing lead solder wire, it is hoped to choose solder wire with low residue and smoke concentration.
Tin content: This is the most important part and the only criterion for judging the grade of solder wire. It is also related to important factors such as welding effect, robustness, reliability, and conductivity. When we use leaded solder wire, we must use solder wire with tin content that meets the product requirements, otherwise the soldering quality will have different degrees of problems. The amount of tin content can't be distinguished with eyes, only through testing can we know. There are also many kinds of detection methods, such as: spectroscopic detector, gravimetric method, chemical titration method, etc. Electronic factories generally do not have these testing equipment, leaving a large gap.
Packaging appearance and weight of solder wire: Although the appearance cannot accurately explain the problem, it still needs to be mentioned. The products produced by a formal, powerful and branded manufacturer must have relevant appearance packaging standards, and there are detailed instructions for marking the solder wire. There is another thing worth mentioning. It is the weight of each roll, and the price is different for different weights. The current lead-free tin wire has a variety of packaging weights.