What should you pay attention to when using a lead-free soldering iron?
In SMT patch processing, lead-free technology is a basic requirement for the social environment, and lead-free electronic products are the pursuit of green environmental protection. To carry out the lead-free process to the end, the selection of soldering iron is very particular. The melting point of lead-free solder wire is 34°C higher than that of commonly used sn63pb37. It is difficult to perform SMT soldering with a general soldering iron. Even if the power is increased, it is difficult to solder. The main reason is that once a general soldering iron contacts the PCB pad, the temperature immediately drops. Over time, the flux carbonizes and cannot be wetted.
Key points of the lead-free process: Generally, the appropriate soldering temperature is the melting point + 40°C, and the setting temperature of the soldering iron is the melting point + 150°C.
What are the methods for choosing a soldering iron with lead-free process?
For lead-free soldering, you should use a fast temperature-replenishing soldering iron, such as a temperature-controlled soldering iron designed with switching power supply technology. When not welding, it can be maintained at a lower power, and it will instantly recover during welding and have a high power output (power output needs to be variable).
The key to choosing a lead-free soldering iron is not the temperature the soldering iron can reach, but whether it can provide the temperature required for soldering in a short time (the ability to provide the required heat in a short time). There are many better brands of lead-free soldering irons, such as OK, Qianzhu, ERSA, and Baiguang. When using these lead-free soldering irons for SMT chip processing, you should pay attention to the following 5 points:
(1) Before use, the temperature of the soldering iron should be set to 250°C, and the soldering iron tip should be pre-treated (tinned).
(2) The optimal SMT welding temperature is 350°C. For high-temperature welding above 400°C, the oxidation speed of the soldering iron tip is 2 to 5 times that of 350°C. In order to speed up SMT processing and welding, many operators sometimes set the temperature to 450°C. This is incorrect and will greatly reduce the service life of the soldering iron, and even need to replace a soldering iron tip in three days.
(3) It is strictly forbidden to use sandpaper to polish the soldering iron tip.
(4) Do not apply excessive pressure to the solder joints
(5) Low activity flux should be used
The residue on the lead-free soldering iron tip is mainly tin oxide (unlike lead-containing tin wire, which is mainly flux carbide). It can be restored as long as the carbide on the surface is removed first and the tin plating layer is formed again. This kind of tin oxide cannot be removed with cleaning methods such as sponges. Alumina powder or special flux should be used to remove it. It is strictly prohibited to use files to remove it (iron plating is only 500μm).
