Surface mount assembly(SMT Assembly) is a type of surface mounting components with no leads or short leads (referred to as SMC/SMD) mounted on the surface of a printed circuit board (PCB) or the surface of other substrates , Circuit assembly technology that is soldered and assembled by reflow soldering or dip soldering.

SMT Assembly Process:

1) Dispensing: Since most of the circuit boards currently used are double-sided patches, in order to prevent the components on the input surface from being melted and re-sold off due to the solder paste re-melting, it is necessary to install a dispenser on the input surface. The main function of water droplets to the fixed position of the PCB is to fix the components to the PCB. The equipment used is a dispenser, located at the forefront of the SMT production line or behind the inspection equipment. Sometimes because customers require dispensing on the output side, many small factories now do not use dispensers. If the input surface components are large, manual dispensing is used.

2) Mounting: Its function is to accurately install surface-mounted components to a fixed position on the PCB. The equipment used is a placement machine, located behind the printing machine in the SMT production line.

3) Curing: Its function is to melt the patch glue, so that the surface assembled components and the PCB board are firmly bonded together. The equipment used is a curing oven located behind the placement machine in the SMT production line.

4) Reflow soldering: Its function is to melt the solder paste, so that the surface assembled components and the PCB board are firmly bonded together. The equipment used is a reflow soldering furnace, located behind the placement machine in the SMT production line.

5) Cleaning: Its function is to remove the harmful welding residues such as flux on the assembled PCB board. The equipment used is a washing machine, and the location may not be fixed, either online or offline.

6) Inspection: Its function is to inspect the assembled PCB board's welding quality and assembly quality. The equipment used is a magnifying glass, microscope, online tester (ICT), flying probe tester, automatic optical inspection (AOI), X-RAY inspection system, functional tester, etc. The position can be configured in a suitable place on the production line according to the needs of inspection.

7) Rework: Its function is to rework the PCB board that detects the failure. The tools used are soldering iron, rework station, etc. Configured anywhere in the production line.

Introducing some assembly methods of SMT:

SMT is currently one of the most popular electronic product assembly methods.From the early 1960s to the present, SMT equipment has experienced manual to semi-automatic to fully automatic, the accuracy has been improved from the previous millimeter level to the current micron level, and SMT components have gradually become thinner and shorter Direction development. The process difficulty of SMT continues to deepen, and the process technology has gradually matured, including lead-free process (Lead free) and 0201 or even 01005 component technology.