Surface Mount Technology (SMT) – Application, Advantages, Disadvantages

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Surface Mount Technology

What is Surface mount technology?

Surface mount technology can achieve higher packing densities, higher reliability, and reduced cost compared to the plated through-hole insertion process. Currently, this technology is the most widely used process for high production, consumer electronics assemblies.PCBA method is ideal for small circuits and components. This is a fully automated Surface mount technology that can achieve higher packing densities, higher reliability, and reduced cost compared to the plated through-hole insertion process. Currently, this technology is the most widely used process for high production, consumer electronics assemblies. Thus, a pick and place machine can easily pick and place the components on the PCB. There are three main steps in the PCB assembly process. First, the printed circuit board receives a generous application of printer-grade solder paste. Then all the necessary components are installed in their respective locations. Finally, the board goes through a 500-degree oven which liquefies the solder paste and thus seals all the components in place.

 Surface mount technology can achieve higher packing densities, higher reliability, and reduced cost compared to the plated through-hole insertion process. Currently, this technology is the most widely used process for high production, consumer electronics assemblies. Instead of putting lead wires through drilled holes in the circuit board, components and elements are mounted directly to the surface of the board in SMT technology.

 Difference between through process and surface mount technology

 When designing a printed circuit board (PCB), one of the first decisions you will make is selecting the type and style of components to use. 

 In the past, components with long conductors were usually inserted manually into the through-hole plated on the PCB. The wires would then be soldered to form permanent interconnections with the holes. This was known as a through a joint. Increasingly, designers such as PCBASIC designer prefer to use an (although now fully mature) assembly method, which uses components whose wires attach only to the surface of the PCB, without the need for a mating hole. This method was first known as “flat mount” and later became widely known as surface mount technology. 

 In some processes, the components are lead-free and are mounted directly to the surface of the board. In the through-hole, the element has wires connected to the wiring board the through-hole.

 The components of Through-Hole technology are larger, resulting in a lower component density per unit area. The packaging density that can be achieved with SMT PCB is very high as it allows components to be mounted on both sides when needed.

 Appliсаtіоn of Surface Mount Technology On PCB

 The Application of SMT Technology in Electronic Printed Circuit Board Manufacturing this technology simply means that electronic components are assembled by automated machines that place them on the surface of a board (printed circuit board, PCB Unlike traditional through-hole processing (THT), SMT is the most common process used in the electronics assembly industry. SMT process is almost entirely used in the assembly and manufacture of printed circuit boards. 

 Surface mount components are smaller and generally offer better levels of performance, and can be used with automatic pick and place machines, in many cases eliminating the need for manual intervention during assembly. Wire components are also difficult to place automatically because the wires must be performed to match the proper hole spacing, and even then they are prone to problems when placed.

 During PCB assembly, most of the circuit board components are automatically placed. Sometimes some may require manual intervention, but it has gone down. Traditionally, some connectors and other components require auxiliary placement, but the level of manual placement6 has declined.

Advantages and disadvantages of surface mount technology:

In industry SMT has largely replaced the through-hole technology construction method, that is, the printed circuit board with wire components in the hole.

Advantages

• Miniaturization

The geometric size and volume of electronic components in PCB SMT are much smaller than that of through-hole interpolation components. Generally, the through interpolation components can be reduced by 60% ~ 70%, and some components can even reduce their size and volume by 90%. Meanwhile, the component weight can be reduced by 60-90%.

• High signal transmission speed

SMT assembly components not only have a compact structure but also a high-security density. When the PCB is glued on both sides, the assembly density can reach 5-5-20 solder joints per square centimeter. This technology can realize high-speed signal transmission due to short circuits and small delays. Meanwhile, SMT assembled circuit boards are more resistant to vibration and shock. It is of great importance to realize the ultra-fast operation of electronic equipment.

• High-frequency effect

 Because the element has no threads or the threads are short. Circuit distribution parameters are reduced and RF interference is reduced.

• SMT manufacturing is beneficial for automatic production, improves production yield and efficiency.

Standardization, serialization, and consistency of soldering conditions of chip components allow SMT assembly to be highly automated. Component failure during welding is greatly reduced and reliability is improved.

• Lower material

 Most SMT components cost less to package than THT components of the same type and function due to the increased efficiency of production equipment and reduced consumption of packaging materials. So the selling price of SMT is lower than that of THT components.

 • Simplify production processes and reduce production costs.

 When installed on the PCB, there is no need to bend, shape or shorten the lead wire of the components, which shortens the whole process and improves the production efficiency. The processing cost of the same functional circuit is lower than through interpolation, which can generally reduce the total production cost by 30% -50%.

 Disadvantages

 • Small spaces can make repairs more difficult.

 • It does not guarantee that the solder joint will resist the compounds used in the potting process. Connections may or may not be broken during thermal cycling.

 • Components that generate large amounts of heat or withstand high loads should not be surface mounted as the solder melts at high temperatures.

 • The weld also weakens due to mechanical stress. This means that the components that will interact directly with the user must be wired using the physical link installed through the hole.

Conclusion:

 Surface mount technology is the method of attaching electronic components to the surface of the PCB. It welds the surface mount assembly to the plate by reflow soldering. The surface assembly process begins at the design stage, where many different components are selected and the PCB is designed using software packages such as Orcad or Capstar.

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