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What does SMT mean in the electronics industry?

SMT is surface assembly technology (surface mount technology), called surface mount or surface mount technology. It is currently the most popular technology and process in the electronics assembly industry.

It is a method of installing leadless or short-lead surface-mounted components (referred to as SMC/SMD, called chip components in Chinese) on the surface of a printed circuit board or other substrate, through Circuit assembly technology using reflow soldering or dip soldering and other methods to solder and assemble circuits.

The SMT/MES industry is based on three pillars. China's SMT/MES industry is mainly concentrated in the eastern coastal areas, including Guangdong, Fujian, Zhejiang, Shanghai, Jiangsu, Shandong, Tianjin, Beijing and Liaoning. The volume accounts for more than 80% of the country.

By region, the Pearl River Delta and surrounding areas are the strongest, followed by the Yangtze River Delta region and the Bohai Rim region third.

Although the total amount of SMT/MES in the Bohai Rim region is far behind that of the Pearl River Delta and the Yangtze River Delta, it has huge growth potential and stronger development momentum. Relevant national departments announced that Binhai New Area in Tianjin will become the third pole of my country's economic growth after Shenzhen and Shanghai Pudong.

Extended information:

Assembly process:

SMT assembly process is closely related to every process step before welding, including capital investment, PCB design, components Solderability, assembly operations, flux selection, temperature/time control, solder and crystal structure, etc.

1. Solder

The most commonly used solder for wave soldering is crystalline tin-lead alloy: tin 63%; lead 37%. The temperature of the solder in the soldering pot should be controlled at all times. Its temperature should be 183°C higher than the alloy liquid temperature and make the temperature uniform. In the past, a solder pot temperature of 250°C was considered the "standard".

2. Wave crest

In the wave soldering process, the wave crest is the core. The preheated, flux-coated, contaminant-free metal can be sent to the welding workstation through a conveyor belt, contacted with solder at a certain temperature, and then heated, so that the flux will react chemically, and the solder alloy will form interconnections through wave crest power. is the most critical step.

3. Cooling after welding

A cooling workstation is usually added to the tail of the wave soldering machine. The purpose is to limit the tendency of copper-tin intermetallic compounds to form solder joints. Another reason is to accelerate the cooling of the components and prevent the board from shifting when the solder is not completely solidified.

Reference: Baidu Encyclopedia-SMT