What Is SMT?

Publish Time: January 05,2019

SMT patch refers to a series of technological processes that are processed on the basis of PCB. PCB is abbreviated as printed circuit board. SMT is surface assembly technology and the most popular technology and process in the electronic assembly industry. It is a circuit assembly technology that installs lead-free or short-lead surface-mounted components on the surface of a printed circuit board or other substrates, and then solders and assembles them by reflow soldering or dip soldering. Under normal circumstances, the electronic products we use are designed by PCB plus various capacitors, resistors and other electronic components according to the designed circuit diagram, so all kinds of electrical appliances require various SMT processing techniques to process.

SMT basic process components

1. Silk screen: Its role is to print solder paste or patch glue onto the PCB pads, to prepare for the welding of components. The equipment used is a screen printing machine, located at the forefront of the SMT production line.

2. Dispensing: It is to drop the glue onto the fixed position of the PCB. Its main function 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.

3. 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 screen printing machine in the SMT production line.

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

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

6. Cleaning: Its function is to remove the harmful welding residues such as flux on the assembled PCB. The equipment used is a washing machine, and the location may not be fixed, either online or offline.
7. Inspection: Its function is to inspect the assembled PCB'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, function tester, etc. The position can be placed in a suitable place on the production line according to the needs of inspection.