What Does SMT Mean?

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May 10, 2021|Product Innovations and Design

What Does SMT Mean?

SMT is the acronym for surface-mount technology. It is a method where electrical components are mounted straight onto the surface of a printed circuit board, also known as PCB. 

SMT, or Surface Mount Technology, is the common working acronym detailing the method whereby electrical components are mounted directly to the surface of a PCB, or printed circuit board. Today’s commercially made electronics are filled with tiny devices that would be impossible to craft with traditional components and human hands. Unlike the system of wire leads that are occasionally used for home kits, SMT allows components to be directly mounted to the surface of printed circuit boards.

Almost all of our electronic equipment is manufactured with this technology. SMT offers significant advantages in cost, production, and labor, and has changed the manufacturing industry since the 1970s. The size, automation, and assembly afforded by SMT has brought significant improvements to the reliability of electronics as well as enormous overall financial savings.

Instead of being created with leads and wires, SMT components are set on PCBs and soldered directly to the boards. SMT package styles include passive components, transistors and diodes, and integrated circuits. With so many categories of SMT components, it’s possible for manufacturers to create the exact PCBs that customers need. Advancements in surface-mount technology have allowed a huge variety of components to become available, far exceeding what was once possible in traditionally leaded forms. Surface-mount technology has helped many different industries flourish in the last 50+ years.

SMT is a machine-automated process that eliminates human errors and comes with a host of advantages that benefit the manufacturing process. It’s quicker and more cost-efficient to run an SMT process, with decreased mistakes and lower overhead. Also, because of the smaller size of surface-mount technology, products can be more compact. With smaller internal components come less external packing, minimal size, and technological advancements.

There are many benefits that come with utilizing SMT. There are many environmental advantages to this technology, such as lower resistance at its connection points, better flexibility when building printed circuit boards, improved automation, increased density of components, smaller and lighter boards, fewer drilled holes, easier assembly, and overall better performance. Surface-mount technology allows for a more efficient PCBA, which means mass production across thousands of industries.

Evolution of Surface-Mount Technology

There are two main manufacturing techniques at one’s disposal during the PCBA (Printed Circuit Board Assembly) process. Through-hole technology is required in certain instances, but is used less frequently—through-hole designs are more inconvenient to build.

Most PCB manufacturers are more than equipped to handle any through-hole project. Candor specializes in SMT or Surface Mount Technology, which enables us to build high-quality circuit boards that require less time and have fewer errors. There are many advantages that come with surface mount tech, but how did the technology come to be? Customers might be interested to know how SMT was conceived, how it continues to evolve, and how it benefits the PCB industry.

Through-hole technology evolved into Surface Mount Technology in the 1970s after being developed in the 1960s. While through-hole assembly is touted as the alternative method for PCBA, until the 1960s it was the only option available to manufacturers. It continues to be a reliable method of assembly, though the process has become too time-intensive, making it difficult for assemblers to keep up with demand. As technology shifted over time and circuit boards became more and more coveted across industries, SMT was born as the electronic manufacturing industry’s response to this change.

Surface Mount Technology: A History

After initial development in the 1960s, SMT was fully integrated into PCB manufacturing and assembly throughout the 70s and 80s. This automated assembly method allowed PCB assemblers to provide quicker turnaround times on the same quality PCBs at lower labor costs. Plus, SMT created new opportunities for higher-density PCBAs, such as double-sided PCB assemblies and assemblies requiring greater volume.

Surface Mount Technology continues to be utilized as technology advances. By using SMT, manufacturers have been able to produce micro-assemblies with smaller and smaller PCB components. SMT allows components to be soldered automatically, meaning the PCBA doesn’t require as much space between components. With smaller components assemblers have less room for error, meaning that SMT had to become more prevalent than through-hole technology. Surface Mount Technology allows industry strategies that avoid overheated PCBs, fault soldering, and other mistakes.

The Future Of SMT

Surface Mount Technology has enjoyed a lengthy history, while still undergoing many required changes as the demands of PCBAs have increased. It’s natural for industries, customers, and manufacturers to question how this technology will continue to evolve to meet the demands of an ever-changing future. A widespread concern for PCBA is related to the environmental sustainability of these projects. While technology continues to adapt to new industry standards, SMT processes have been reworked to accommodate RoHS (lead-free) solders. PCB manufacturers and assemblers continue to work to meet their customers’ needs as SMT processes evolve.

The vibrant history of SMT innovation has allowed the PCB industry to flourish, in turn making many technologies and products possible. SMT continues to be built upon industry needs, with manufacturers keeping pace with innovations in order to provide the best services possible.

Comparison with Other Technologies

Through-Hole vs. Surface Mount

The through-hole mounting process is where component leads are placed into holes drilled into a bare PCB. While this was standard practice until the 1980s, it was expected that SMT would completely phase out its common use. Despite its severe drop in popularity and practicality, through-hole tech has remained resilient—it offers its own advantages and niche applications that SMT does not.

Through-hole is a reliable process best used for products that require stronger connections between layers. SMT components are secured by surface board solder, while through-hole components run through the board via leads, allowing them to withstand higher environmental stress. Because of this, through-hole technology is commonly used in aerospace and military products that experience extreme collisions, temperatures, accelerations, and weathering. In addition, through-hole tech can be useful to test and prototype applications that might require manual adjustments or replacements.

While through-hole might not be as widely used as it once was, it hasn’t disappeared completely from PCBA. There are factors such as availability and cost that govern whether or not a manufacturer uses SMT or through-hole—not all components are available, and sometimes through-hole technology is less expensive. It might be a secondary option, but it’s paramount that it remains available as a choice for manufacturers.

Surface Mount Technology allows components to be mounted directly to the surface of the printed circuit board. Developed in the 1960s as a process called “planar mounting,” SMT has become very popular since its mainstream use in the 1980s. Virtually all electronic hardware these days is mounted via this process. It’s essential to PCB design, and manufacturers have improved the quality, performance, and volume of PCBs while reducing costs in labor, processing, and handling.

SMT and through-hole mounting have key differences:

• SMT components are smaller
• SMT doesn’t require holes to be drilled through the PCB
• SMT components can be mounted on both sides of the board.
• SMT allows a high number of small components for denser PCBs with higher performance.

Through-hole component leads run through the board and connect a board’s layers are replaced by small components called “vias” that allow a conductive connection. These connections between the different PCB layers essentially act as through-hole leads. There are some surface mount components, such as BGAs, that are higher-performing components with more interconnection pins which allow higher speeds.

Advantages: Because of SMT’s automation, this technology enables smaller PCB size, higher component density, and more space to work with. SMT requires fewer drilling holes, meaning there is a lower cost and faster production time overall. SMT components can be placed at thousands and tens of thousands per hour during assembly, versus less than a thousand per hour for THM. Because programmed reflow ovens make solder joint formation on PCBs more reliable and repeatable, through-techniques are less appealing and less viable. In addition, SMT improves performance and stability, especially in shake and vibration conditions.

Disadvantages: SMT can be occasionally unreliable when used as the sole attachment method, especially for components that are subjected to mechanical stress. Through-hole technology is better for external devices that are frequently manually attached and detached.

SMT is almost always more efficient and cost-effective than THM. It’s used in the vast majority of manufacturing today—over 90 percent of PCBAs use SMT. Still, there remain special instances of mechanical, electrical, and thermal manufacturing that require the through-hole process, meaning that it will be a relevant secondary option for years to come.

SMT vs. Chip-on-Board (COB) Technology

Chip-on-board assembly differs from SMT by installing the bare semiconductor chips directly on the PCB. By using non-conductive or conductive epoxy, the manufacturer can incorporate aluminum wedge bonding or gold ball boding to achieve an electrical connection.

COB allows the systems designer to have unique assembly options not available through SMT. The silicon die is then glued directly to the surface of the PCB to establish an electronic connection, and a coating of epoxy resin is placed over the die to protect it against shocks and light.

Chip-on-board is a great option for miniaturized circuits and LED circuits, because it provides a better solution when traditional assembly tech can’t meet the required design parameters.

Benefits of COB technology:

• Enables high or low-voltage design
• Custom coatings available
• Double-sided multi-layered boards
• High or low-volume functional board testing
• A wide array of temperature ranges

Chip-on-Board tech is “advanced” SMT, as their major difference is that COB involves a high lead count, active devices, and doesn’t require ceramic or molded plastic protecting the outer device packaging.

Advantages: COB minimizes the weight of a circuit, meaning that when weight is a major factor chip-on-board assembly is the ideal solution. COB also provides enhanced protections against reverse engineering, lower costs, improved performance results, minimized space requirements, greater reliability because of heat distribution, a wider application range, and a smaller number of solder joints. COB also has a higher production efficiency than SMT.

Disadvantages: COB LED packages feature a higher maintenance cost and a lower pass rate. They also feature higher manufacturing costs because of their higher defect rate. COB and SMT also feature a different light source quality for LEDs since SMTs are multiple-point light sources attached together and COBs feature more uniform illumination.

Other Common Abbreviations

There are many different ways to discern the components of surface-mount technology. Inclusive of that are many acronyms for the internal makeup of the surface-mount technology, including the following:

SMD

This acronym is in regards to surface-mount devices. SMDs are the electromechanical, passive, and active components within the SMT. These items are the primary makeup of the device.

SMA

Surface-mount assembly is the long-form name for SMA. Surface-mount assembly is the process of creating something utilizing surface-mount technology. It is how a device is made using SMT.

SMC

This set refers to the surface-mount components, a blanket term for the items you will find inside surface-mount technology. These are the items that allow the device to operate, much like SMD. 

SMP

When you have surface-mount packages, also known as SMP, you have a case or device that keeps all the components. This package is similar on a larger scale to a computer tower case or the outer shell of a cell phone.

SME

Surface-mount equipment is what SME stands for and defines the mechanical products used to assemble surface-mount technology. These are the intricate pieces of machinery that help attach all necessary elements. 

SMT Devices

As referenced in the abbreviations section, SMD (surface-mount devices) are the electromechanical, passive, and active components. But what do all of these categories consist of? This brief list will give you more insight.

Electromechanical

When you see the category of electromechanical, it pertains to the connectors and relays. These components allow for the energy to move correctly within the device.

Passive

There are three main parts when it comes to passive SMD. Those are resistors, capacitors, and inductors. Passive SMD typically comes pre-packaged, which makes them easier to install. 

Active

When looking for the active components in surface-mount technology, you will typically find integrated circuits. Integrated circuits are groups of chips residing on a single chip. 

SMT Applications

When applying surface-mount components onto a board, you have to use great care. Soldering such small items is an arduous and delicate task, so specialized equipment is necessary if you’d like to do so. Application is possible in different ways, as was done in the past. However, manufacturing them in this way is done due to the significant cost savings associated with the process. 

SMT Advantages

SMT comes with an arsenal of advantages and is beneficial in many areas of life. Not only is it much quicker to manufacture and highly cost-effective to set up and run, but it also leaves less room for error. Surface-mount technology is machine automated, eliminating sleight of hand mistakes. 

Additionally, the smaller size that surface-mount technology produces makes the overall product much more compact. Smaller internal components allow for the external packing and size to be more minimal.   

As an environmental health benefit and advantage and a quality perk, surface-mount technology uses lower resistance and inductance at the connection point. As a result, there are fewer unwanted radio frequency effects. This reduction makes for a better and more predictable high-frequency performance. Using SMT emits lower radiated emissions due to the smaller radiation loop area and lesser lead inductance.

SMT Disadvantages

Although surface-mount technology has many advantages, it isn’t always the best option for every circumstance. 

In the case of error or breakage, surface-mount technology component repair is more complicated and requires a high skill level and expensive tools. This level of detail is due to the small sizes and the lead spacings of several SMD types. If you need to handle small SMT components, it will require tweezers. This method is unlike the one for through-hole components, which consistently stay in place. 

Additionally, you can’t typically install surface-mount technology components in sockets. This method is often utilized for easy installation or component repair upon an instance of failure. When using through-hole components, this is usually an option to use. 

PCB Assembly Using SMT

Printed Circuit Board (PCB) creation previously included tedious and arduous tasks. Oftentimes, many errors would happen during PCB manufacturing, and it would require the manual assistance of a factory worker or operator to fix.

Manufacturers overwhelmingly welcomed surface-mount technology to PCB production.PCB assembly using SMT significantly reduced the margin of error in the process. Not only did this allow for less human intervention, but it began increasing production. Additionally, labor costs began to decline due to the efficiency of the work.

What Is the Difference Between SMT and SMD?

Although the surface-mount devices (SMD) are the functional components that allow the end product to operate, the surface-mount technology utilizes automation to apply the SMD to its designated board. Like a car factory, where mechanical processes construct pieces of a larger product, surface-mount technology builds parts on a much smaller scale. 

The use of surface-mount technology allows for the SMD to remain small in size. The technology can allow this due to the intricate mechanics that comprise the robotic automation device.

Conclusion

Every day new technology is introduced to the world. Each fulfills a specific purpose and tries to make existing processes simpler. 

Surface-mount technology is no exception. With the inclusion of this new technique, in-demand items are coming off the line at a much quicker speed. Additionally, the costs previously associated with the production of such products are consistently declining. With lessening labor costs due to faster and more efficient technology, producing the same item is vastly different across the board.

Surface-mount technology is a welcome process that has incorporated incredible benefits to many different areas of life. This new technology has afforded the world to propel forward in ways that were previously impossible.