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The History of Surface Mount Technology

An increasing number of manufacturers are embracing surface mount technology (SMT) in the assembly of printed circuit boards. The growth of SMT began in the 1980s, although the technique had been around for two decades prior to this.

SMT is a process of mounting electrical components directly onto the printed circuit board’s surface. A component mounted in this way is known as a surface-mount device. This method has largely replaced the through-hole technology approach.

Surface Mount Technology

© Gorodenkoff / Shutterstock

 

History of SMT

The use of surface mount technology began in the 1960s, when it was originally called “planar mounting”. First demonstrated by leading American computer manufacturer IBM in 1960, in a small computer; the design was later applied in the Launch Vehicle Digital Computer used by NASA for its space programme.

SMT was used in the instrument unit that guided Saturn V vehicles – the heavy-lift launch rockets used by NASA, from 1967 to 1973, in the Apollo programme for exploration of the moon. It was later used in the Saturn 1B rocket that launched the Apollo spacecraft into orbit in 1973, during training for manned flights to the moon.

Saturn 1B also launched the first American space station, Skylab, in May 1973. It was later used in the 1975 Apollo-Soyuz Test Project – the first crewed international space mission completed jointly by the US and the Soviet Union.

Despite its auspicious beginnings, surface mount technology didn’t become popular until the mid-1980s. As recently as 1986, surface mounted components represented only around 10% of the total market.

However, the technique took off in the late 1980s and most high-tech electronic printed circuit boards were using surface mount devices by the late 1990s. Today, SMT is widely used in the vast majority of applications.

 

How SMT works

Components are designed with small metal tabs that are soldered directly to the surface of the PCB. This led to the components becoming much smaller – currently, the smallest is called 01005, and it measures just 0.4 x 0.2 mm!

Placing components on both sides of the board has become far more common with surface mounting than with through-hole mounting. This permits smaller circuit boards and much higher circuit densities. In turn, the sub-assemblies and machines containing the boards can also be smaller.

Thanks to the ever-changing technology, manufacturers have a greater ability to create high-quality work in a much smaller area.

 

Advantages of surface mount technology

There are many benefits to using SMT. Significantly, it reduces the need for human intervention and thus has less chance of errors. This also reduces labour, production and overhead costs.

The repetitive operations support a more effective process of quality control. Previously, the quality was checked post-production. Today, more advanced prevention techniques are used: the components from the first part of the process, and the first products from the run, are inspected and confirmed.

SMT increases the operating and production speed, while increasing the circuit density and capabilities. The technique reduces heat generation and power consumption during production. Notably, surface mount is useful when used in combination with through-hole techniques.

The surface tension of the molten solder will pull the components into alignment with the solder pads, correcting small errors in component placement automatically. This process enables lower resistance and induction at the connection, providing better high-frequency performance, while reducing the unwanted effects of RF signals.

 

Disadvantages of surface mount technology

While there are many benefits to using SMT, it also has some disadvantages, including the fact it can be costly investing in the machinery.

The solder connections can sometimes become damaged due to the potting compounds going through thermal cycling; small spaces can make repairs more difficult; the solder can also be weakened by mechanical stress, so the components that will directly interact with the user may need to be attached using through-hole mounting.

However, the disadvantages tend to be outweighed by the advantages, largely because SMT enables increased manufacturing automation, reduced costs and improved quality.

 

Why choose Sellectronics’ SMT?

Sellectronics’ surface mount technology board assembly lines are powered by state-of-the-art systems; two lines, with a combined placement rate of 75K per hour, from 01005 to 70mm² devices.

Our assembly process involves the surface mount devices being machine picked and mounted directly onto the PCB’s surface, which enables thousands of electrical components to be attached in a relatively short time; skilled engineers guarantee the highest quality finished products, using lead-free solder paste and Automatic Optical Inspection at every stage.

Contact us to discuss your next electronics manufacturing project.

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