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Surface Mount Technology: Overview

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Almost every electrical device contains printed circuit boards. Their integral part consists of electronic components mounted on a PCB. We can mention two ways of placing elements on a PCB with a printed circuit, namely surface mounting and through-hole mounting. In this article, we explain what SMT is, which is entirely automatic in most cases.

Surface mount technology has been rapidly developing since the 1970s. It is now an integral part of the entire electronics industry. Surface mounting gradually replaces coated mounting as we strive to miniaturize devices and their components. SMT is a guarantee of the high packing density of components on printed circuit boards.

What does Surface Mount (SMT) mean?

STM is a way of placing components on a PCB. Electronic elements (surface mount devices–SMDs) are glued directly to the PCB, and if necessary, SMD can be embedded from both sides. Components for surface mounting are small in size, have flat housings, and solder tips in the form of so-called flanges that span the ends of the housing.

When assembling this type of mounting, you need to be very precise when arranging individual electronic components on the pads. Therefore, SMT takes place on the appropriate production lines. SMT assembly machines work very quickly and with extreme precision. Thanks to this, it maximizes the possibility of introducing automation to large, serial production.

What is the SMT assembly process for PCBs?

During SMT surface mounting, the PCB goes through four stages:

Stage one: Applying the solder paste

The paste with the consistency of thick grease is applied to the solder pads using special printers equipped with a template prepared in advance. The solder paste stencils have pre-cut holes that are ideally suited to the solder pads.

Stage two: Arranging elements collected from feeders on a PCB

At this stage, the pick & place machine takes SMD elements from the erector and places them in the appropriate places on the printed board. These devices are fast and precise.

Stage three: Multi-profile furnace brazing

The third step is to melt the solder paste in a reflow oven. The surfaces wetted with solder binder create permanent solder joints. The suitable viscosity and consistency of the solder paste affect the quality of the print. You can also use glue to fix the elements. Then it will be necessary to use a steel template for glue application.

Stage four: Assembly quality control at AOI

The last step is AOI (Automated Optical Inspection). It is also possible to carry out inspections by employees or with the use of X-ray machines.

Advantages of Surface Mount for PCB Design

AUTOMATION OF THE PROCESS

That is the main advantage of surface mounting. As a result, this assembly system influences the speed and efficiency of PCB production.

MINIATURIZATION

SMT technology allows you to minimize the size and weight of the entire PCB. The surface mounting system also allows the assembly of elements on both sides of the board. Thanks to this, arranging more components in a limited space is not a problem.

Technology leaders strive to create a connected society, and size matters when it comes to PCB design. In our quest for the ubiquitous data processing, Internet of Things, or the “ambient intelligence” we all crave, the quest to create ever-smaller pieces extends to the very heart of electronic devices, the board.

LOWERING PRODUCTION COSTS

Smaller components allow you to create smaller PCBs, and we can fit them into almost any shape. Smaller sizes mean less to produce, leading to cost reductions in the manufacturing process.

SMT also reduces production costs because it is carried out in a fully automated manner. Of course, you should remember that in order to create a production line, you have to invest in appropriate machines. That can affect your company’s operating costs at first. It’s worth the price. In the long run, surface mount technology improves overall production efficiency and effectively reduces the cost of the work.

HIGH RELIABILITY

From the moment the prototype is authenticated, all surface assembly is virtually automatic. The operation of the machines is practically flawless. Automation also eliminates the risk of human error. Thanks to automation, SMT technology guarantees PCB consistency and reliability.

Conclusion

We currently use automatic surface mounting in many electronic devices. It becomes an impulse for innovative technological solutions. Thanks to STM, electronic devices are widely used in all types of industry. However, SMT has one significant drawback. If there are any errors during the automatic assembly on the tape, manual repair of such elements is significantly laborious or even impossible. For this reason, SMT is usually not used in the production of short series due to the low cost-effectiveness of such a solution.

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