SMD Welding | Surface Mount Welding Guidelines

SMD Welding | Surface Mount Welding Guidelines

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

SMD welding and desoldering are almost the same as through hole welding and desoldering.
SMD desoldering is usually completed with hot air blower, while welding can be completed with 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. As the convection dominated IR welding has a high yield and low operating cost, it has developed into the preferred process for 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 batch production in the factory, SMT machine is used for SMD welding. The main type of machine is reflux furnace

Reflux furnace machine
The most widely used reflow soldering processes in electronic products are:
Vapor phase; And infrared.
Manual SMD welding process
Use soldering iron or soldering station, hot air SMD repair station, 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, using SMD electronic components and through hole electronic components to assemble different types of PCB, the use of through hole components will continue in the foreseeable future. For via 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 widespread use of low solid content or no cleaning flux. However, nitrogen should not be expected to be the 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 choice of welding process depends on the mix 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)


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