1. Working temperature:
Sn63/Pb37 lead-tin bar suggested working temperature: 255±10℃.
2. Removal of scum in wave soldering
Dross is an oxide that forms on the surface of the solder at a rate dependent on temperature and agitation. The higher the temperature and the greater the turbulence on the solder surface, the more dross will be formed. Antioxidants can also be added to form a protective film on the tin surface to reduce tin oxidation.
Oxides on the solder surface prevent re-oxidation of the solder, so frequent removal of scum is not necessary. Cleaning once a day is fine as long as it doesn't interfere with the propulsion of the waves. You can also push the tin slag to a corner, add reducing powder on the tin slag and stir it to reduce most of the hip-hop to tin.
3. Addition of new tin bars in wave soldering
During the wave soldering process, the tin content will continue to decrease. When it decreases to a certain extent, new tin strips should be added in time to maintain the tin liquid level, thereby reducing the increase in tin oxidation due to the large drop of tin liquid.
4. Removal of impurity Cu (with lead); regularly detect the composition of solder in the tin furnace (lead-free)
When Cu exceeds its solid state in Sn, an intermetallic compound will form between Cu and Sn, generally Cu6Sn5. The melting point of this compound is above 500°C, so it exists in solid state. Excessive Cu-Sn intermetallic compounds will seriously affect the welding quality.
5. The specific gravity of traditional Sn-Pb solder is 8.4, and the specific gravity of tinned copper impurity Cu6Sn5 is 8.28.
Therefore, the "specific gravity method for copper discharge" can be used in the lead process. That is, lower the temperature of the tin furnace to about 190°C (the tin-lead solder is still not liquefied at this time), then stir the solder for about one minute, and then let it stand for more than 8 hours. Since the specific gravity of Cu6Sn5 is smaller than that of tin-lead solder, the compound will float on the surface of the solder, and the upper impurity will be removed, and the impurity Cu will be removed. Cu can be removed once in half a month or a month or so, which can reduce the number of slot changes and reduce costs.
The specific gravity of lead-free solder is generally about 7.4, which is smaller than that of tinned copper. The impurities of tinned copper will sink to the bottom of the furnace, so it is impossible to remove impurity copper by "specific gravity method of copper discharge" like the lead process. Therefore, the composition of the solder in the tin furnace should be checked regularly, and when copper and lead are found to be close to the maximum allowable standard, the solder should be replaced in time. Depending on the customer's output, it is recommended to clean the furnace once every 4-6 months.
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