SMD welding - Surface Mount welding guidelines

SMD welding - Surface Mount welding guidelines

Learn how to weld SMD in this detailed surface mount welding guide.

SMD welding and disassembly welding are almost the same as through-hole welding and disassembly welding.

SMD disassembly welding is usually completed by hot air blower, while welding can be completed by soldering iron and solder wire or solder paste or solder ball (BGA) and SMD hot air blower / repair bench.

SMD welding process type

All SMD welding processes have technical problems, and there are methods to solve these problems. Because the convection dominated IR welding has high yield and low operation cost, it has developed into the preferred process of convection welding.

Vapor phase welding will not disappear, but will continue to be used in special occasions. For some professional work, other reflow welding processes are also used, such as laser and hot rod resistance welding. The purpose of these welding processes is not to replace gas phase or infrared, but to supplement them. The final process used shall be selected according to the specific requirements of the intended application, solder defect results and total cost.

SMD welding process for mass production

For mass production in the factory, SMD welding is carried out by SMT machine. The main type of machine is the reflux furnace

Reflux furnace machine

The most widely used reflow soldering process in electronic products is:

Vapor phase; And infrared.

Manual SMD welding process

Use soldering iron or soldering table, hot air SMD repair table, solder wire and solder paste for manual SMD welding. This process is mainly used for repair / rework.

Selection of welding process

As the electronics industry will maintain the mixed PCB assembly mode and use SMD electronic components and through-hole electronic components to assemble different types of PCBs, the use of through-hole components will continue in the foreseeable future. For through-hole active and passive electronic components, there is no more cost-effective method than wave soldering. For some applications, solder paste reflow is also preferred.

Nitrogen is widely used in wave soldering and reflow soldering processes due to the wide use of low solid content or cleaning free flux. However, nitrogen should not be expected to be a panacea for solder defects. It will only affect the welding output to a certain extent. Nitrogen will not solve problems related to other parameters, such as design, flux activity, solder paste, printing quality and solder profile.

The selection of welding process depends on the mixing of electronic components to be welded. Various welding processes will complement each other rather than replace them. Even manual welding will not disappear completely.

PCB assembly process flow chart (PCBA process)