What is surface mount technology (SMT) in electronics?-TechSparks (2024)

For electronics enthusiasts, there are often some mystifying acronyms made up of three letters. “SMT,” which TechSparks will introduce in this article, is one such example. So, what exactly is SMT, and why is it so popular? How does it apply to electronics? Let’s delve into these questions with the TechSparks!

As we all know, electronic products rely on a crucial component known as a printed circuit board, often referred to as the “mother of electronics.” Manufacturers utilize PCB to install a multitude of components, optimizing the internal space of electronic devices. However, the process of installing components is not as simple as gluing them onto the board. That’s right, SMT is an assembly technology, and its full name is surface mount technology.

SMT is not a recent development; it has been around for some time and has reached a level of maturity. In traditional PCBA manufacturing, electronic manufacturers used plug-ins to install components on circuit boards. However, as applications became more complex, this method started to exhibit certain drawbacks, such as difficulties in automated production, assembly quality issues, and bulky size. To address these challenges, the industry began exploring new technologies, leading to the birth of SMT.

Accompanying this technology are smaller SMD components, which are affixed directly to a printed circuit board. Unlike plug-in components, SMD components have their leads or terminals remaining on the surface of the board to be soldered. As a result, manufacturers do not need to drill holes in the board and pass the leads through, simplifying the PCB assembly process and allowing for more efficient production.

As mentioned earlier, SMT technology emerged as a replacement for THT assembly, offering distinct advantages:

• Automation: In our world, where tens of thousands of electronic devices are produced daily, efficient and rapid PCBA board production is essential. SMT provides a viable solution through a series of automated equipment in the production line, including connecting tables, picking robots, and solder paste printing machines.
• High Quality: In traditional through-hole assembly, manually inserting component pins into plated through-holes can be error-prone, especially when dealing with complex applications that require dozens or even hundreds of components. SMT assembly, performed by program-controlled machines, ensures consistent and reliable production, resulting in higher-quality PCBA boards.
• Miniaturization: SMT’s use of smaller SMD components, with surface-soldered pins rather than through-holes, allows for significantly smaller component sizes. Designers can arrange these compact components more efficiently, promoting miniaturization trends and optimizing board area utilization.
• High Performance: The shorter pins and closer proximity of SMD components to the PCB reduce signal transmission paths, minimizing inductance and capacitance effects in the circuit. This leads to reduced signal delay, improved working speed, and enhanced circuit response performance.
• Cost-effectiveness: SMT technology’s ability to reduce the circuit board’s size, labor costs, and assembly failure rates make it a cost-effective option for manufacturers.

It is important to note that while SMT has numerous benefits in electronics manufacturing, it does not entirely replace THT assembly. In some cases, through-hole components are still needed to provide enhanced reliability for certain electronic applications. Currently, the utilization rate of SMT technology stands at approximately 70%.

SMT technology uses the form of patch to apply components on the PCB board. The implementation process is as follows:

1. Component Preparation: SMT employs chip components with flat pins, such as integrated circuits, resistors, capacitors, diodes, etc. These components are continuously fed through feeders equipped with absorbent glue or pick-and-place tape.
2. Printing Solder Paste: Solder paste is applied to the PCB stencil, and then a scraper sweeps over the surface, exerting pressure to allow the solder paste to flow through the stencil holes onto the designated positions.
3. Automatic Placement: The automatic placement machine takes components from the feeder and accurately positions them on the PCB, which has been printed with solder paste.
4. Fixing Components: Once component placement is complete, the PCB is conveyed to the reflow oven. In the reflow oven, the high temperature melts the solder paste, enabling the solder to bond with the pads and component pins, securely fixing the components on the PCB’s surface.