Preparation and quality requirements of tin bars

Tin bar, as the name suggests, is a strip of tin solder, which is referred to as tin bar by the industry. Mainly used for wave soldering and dip soldering, it is currently the most consumed variety of electronic solders; a small amount is also used for flame brazing or soldering iron welding of large structural parts and long welds. It is the most important and indispensable connecting material for all electronics, electrical appliances and other products. The global annual consumption is about 100,000 tons.

The preparation process of the tin bar is relatively simple, mainly including the two processes of batching, smelting and casting, and strictly control the degree of oxidation and the content of metal and non-metal impurities. Among them, the two parameters of smelting temperature and casting temperature have a greater impact on the quality of tin bars. The preparation of tin bars is simple and the technical threshold is low, so the competition is extremely fierce. The current pricing only adds a meager processing fee to the cost of raw materials. Once the price of raw material tin fluctuates sharply in the short term, that little profit may be wiped out. , Even loss.

The main requirements for the quality of tin bars are as follows:

1) The surface of the tin bar is smooth;

2) Good fluidity and good wettability during welding;

3) Good mechanical properties;

4) Bright solder joints;

5) Less oxidation residue.

The common defects on the surface of the tin bar are flower spots and blisters. These defects are caused by the manufacturing process and the use of molds. For example, there is no scraping surface during manufacturing, the cooling system is not good, and the mold is not smooth. The cause of blistering is related to the weather at the time of manufacture. The production workers should not use their hands directly when holding the tin bars. The moisture in their hands will affect the brightness of the tin bars. It is best to use cling paper when the tin bars are sent to the plate, so that the brightness can be seen without moisture. When the storage time is long or the storage place is too damp, there will be a layer of oxide on the surface of the tin strip, which will also make the tin strip lighter, but it has little effect on the use effect.