What are the factors that affect the life of lead-free soldering iron tip? How to prolong it
Due to the increase of the melting point of lead-free solder, the working temperature also increases, which leads to a greatly accelerated corrosion rate of the soldering iron tip and a shortened service life. This is a reasonable explanation. When lead-free soldering, the required soldering temperature is much higher than that of ordinary soldering, which is one of the main reasons for shortening the life of the soldering iron tip. The higher the temperature, the faster the oxidation rate. After applying lead-free soldering, why is the service life of the solder tip greatly shortened?
Generally, the solder resistance structure is mainly made of copper inside, and iron (iron plating layer) is plated on the outside, while the front part of the iron plating layer is plated with tin (tin plating layer), and the rear end is plated with anti-oxidation chromium. Since tin and iron are also highly reactive metals, they can easily combine to form mixed metals, especially at high temperatures. Moreover, the flux used in soldering is also a catalyst to accelerate their mixed metal reaction. The rate of generation of mixed metals will vary with different welding temperatures. The higher the temperature, the faster the generation rate, especially at 400°C or above.
When soldering, tin and iron will continue to produce a mixed reaction, and because the resulting mixed metal will peel off from the surface of the tip coating, the tip coating will be gradually eroded away, and then the tin will quickly erode the copper in the tip , will eventually cause the welding nozzle to perforate in a short time.
Solder with different components will have different erosion speeds on the solder tip. The figure above shows: tin + 0.7 copper has the fastest erosion rate on the solder tip, then tin + 3.5 silver + 0.75 copper, tin + 2 silver + 0.75 copper + 3 bismuth, and finally tin + 37 lead. Compared with traditional eutectic solder (67/37 solder), at a soldering temperature of 400°C, lead-free solder: tin + 3.5 silver + 0.7 copper, the corrosion rate of the solder tip is 3 times faster, while tin + 0.7 copper 4 times faster.
■ How to prolong the life of lead-free soldering iron tips
1. When using lead-free solder for soldering operations, due to the heat resistance of the parts and the consideration of safe operation, the set temperature of the soldering iron nozzle is generally expected to be below 350 degrees - 370 degrees;
2. According to the different welding operations of the electric soldering iron, it is very important to choose the most suitable soldering iron tip. A suitable soldering iron tip can reduce the temperature of the soldering iron tip and increase the efficiency of the operation.
3. Different from ordinary water-containing sponges, it is necessary to use metal wires soaked in additives, that is, it does not reduce the temperature of the soldering iron tip, but also plays a cleaning role, and can also remove oxides on the surface of the soldering iron tip. Set the tip of the soldering iron as low as possible.
4. When not in use for more than 10 minutes, the power supply of the electric soldering iron should be cut off.
5. When the tip of the soldering iron is oxidized and blackened, first use solder with flux to remove the oxide. If it cannot be removed, use a dip first.
6. The metal wire cleaner of the penetrating agent removes the oxide on the surface, and then applies new solder.
In addition to corrosion accidents, lead-free soldering also accelerates tip oxidation. Although the formation of lead-free solder joints requires higher temperatures than SnPb solder joints, it is not necessary to increase the temperature of the soldering iron to achieve lead-free soldering in terms of the usual throughput requirements of the industry; however, improved heater control is required to eliminate Temperature overshoot improves the heat conduction efficiency of the solder joint and reduces the idle temperature of the soldering iron. In addition, a more optimized tip shape must be used to avoid excessive temperatures, which would accelerate corrosion of the tip, increasing tip replacement costs and downtime.
