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SMT is surface mount technology (Surface Mounted Technology) (abbreviation for Surface Mounted Technology), and it is the most popular technology and process in the electronics assembly industry. Electronic circuit surface mount technology (Surface Mount Technology, SMT), called surface mount or surface mount technology. It is a kind of surface assembly components with no leads or short leads (SMC/SMD for short, chip components in Chinese) mounted on the surface of a printed circuit board (Printed Circuit Board, PCB) or the surface of other substrates. Circuit assembly technology in which reflow soldering or dip soldering is used for soldering and assembly.
1. What are the advantages of SMT?
SMT was born with the development of the electronics industry,
and developed with the development of electronic technology, information technology, and computer application technology. The rapid popularity of SMT is due to its following advantages.
1) It is easy to realize automation and improve production efficiency.
2) The assembly density of components is high, and the electronic products are small in size and light in weight.
3) High reliability. Automated production technology ensures the reliable connection of each solder joint. At the same time, because the surface mount components (SMD) are leadless or short leads, and are firmly mounted on the PCB surface, they have high reliability and shock resistance. powerful.
4) Good high frequency characteristics. Surface mount components (SMD) have no pins or segment pins, which not only reduces the influence caused by the distribution characteristics, but also firmly attaches and solders to the PCB surface, which greatly reduces the parasitic capacitance and parasitic inductance between leads, so to a large extent Reduce electromagnetic interference and radio frequency interference, and improve high-frequency characteristics.
5) Reduce costs. SMT increases the PCB wiring density, reduces the number of holes, reduces the area, and reduces the number of PCB layers with the same function, all of which reduce the manufacturing cost of the PCB. Leadless or short lead SMC/SMD saves lead material, omits trimming and bending processes, and reduces equipment and labor costs. The improvement of frequency characteristics reduces the cost of radio frequency debugging. The size and weight of electronic products are reduced, which reduces the cost of the whole machine. Good welding reliability will naturally reduce repair costs.
2. What is the basic process of SMT?
The basic process components of SMT include: printing (red glue/solder paste) --> inspection (optional AOI automatic or visual inspection) --> placement (first paste small components and then paste large components: high-speed placement and Integrated circuit mounting) --> Inspection (optional AOI optical/visual inspection) --> Soldering (using hot air reflow soldering for soldering) --> Inspection (Can be divided into AOI optical inspection appearance and functional test inspection) - > Maintenance (tools: soldering station and hot-air desoldering station, etc.) --> board splitting (manual or splitting machine to cut the board)
1) To form an SMT production line, there must be 3 kinds of important equipment: printing machine\dispensing machine, placement machine, reflow oven\wave soldering machine. Among them, the wave soldering process, with the development of surface mount technology, In particular, the large number of applications of bottom-lead integrated circuit packaging BGA\QFN has become more and more insufficient, so the current mainstream is still the reflow soldering process.
