Advantages of SMT Surface Mount Technology
surface mount technology
1. High assembly density
Compared with traditional perforated modules, the area and mass of wafer modules are greatly reduced Generally, the use of surface mount technology can reduce the volume of electronIC products by 60% - 70% and the quality by 75% Through hole installation technology is based on 2.54mm grid; The grid of surface mounted components is developed from 1. The grid of 27mm to 0.5mm current, and the density of instalLED components is higher For example, a 64 pin DIP integrated block has an assembly area of 25mm * 75m, and the same lead uses QFP with lead spacing of 0 63mm, and its assembly area is 12mm * 12mm, which is 1/12 through-hole technology
2. High reliability
Due to the high reliability of chip modules, SMAll and light components have strong impact resistance Automatic production can be used for electronic processing, with high placement reliability Generally, the solder joint defect rate is less than 10 parts per million The wave soldering technology of hole insertion components is one order of magnitude lower The average MTBF of electronic products assembled by surface mount technology is 250000 hours At present, almost 90% of electronic products use surface mount technology
3. Good high frequency characteristics

Since the chip assembly is firmly installed, this assembly is usually lead-free or short lead, which reduces the impact of parasitic inductance and capacitance, and improves the high-frequency characteristics of the circuit. The maximum frequency of the circuit designed with SMC and SMD is 3GHz, and the use of through-hole components is only 500MHz. The use of SMT chip can also shorten the transmission delay time, and can be used for circuits with a clock frequency of 16MHz or higher. If MCM technology is adopted, the high-end clock frequency of computer workstation can reach 100MHz, and the additional power consumption caused by parasitic reactance can be reduced to 1/3 to 1/2 of the original.
4. Reduce costs
The use area of PCB is reduced, which is 1/12 of that of through-hole technology. If CSP is used for installation, the area will be greatly reduced.
The number of holes drilled on the printed circuit board is reduced, and the maintenance cost is saved.
With the improvement of frequency characteristics, the cost of circuit debugging is reduced.
Due to the small size and light weight of the chip components, the packaging, transportation and storage costs are reduced.
SMC and SMD have developed rapidly and their costs have dropped rapidly. The price of chip resistor and through-hole resistor is less than one cent.
5. Promote automated production
At present, if the perforated installation printed board is to be fully automated, the area of the original printed board needs to be expanded by 40% so that the insertion head of the automatic part can be inserted into the component, otherwise the component will be damaged due to insufficient space. Automatic placement machine adopts vacuum nozzle to suck out and release parts. The vacuum nozzle is smaller than the shape of the parts, which can increase the installation density. In fact, small parts and fine pitch QFP parts are produced using an automatic placement machine to achieve automatic production of the whole line.
Of course, there are also some problems in SMT production For example, the nominal values on the components are not clear, which makes maintenance difficult and requires special tools; Multi pin QFP is easy to cause pin deformation and lead to welding failure; The coefficient of thermal expansion between components and printed boards is inconsistent. When electronic equipment is working, solder joints are exposed to expansion stress, which leads to solder joint failure; In addition, the overall heating of components during reflow soldering will also cause thermal stress of equipment, thus reducing the long-term reliability of electronic products But these problems are all problems in development With the emergence of special disassembly equipment and new low expansion coefficient printed boards, they are no longer an obstacle to the further development of SMT

The above is the explanation given by the editor of PCB circuit board company.
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