Every modern electronic device—from smartphones to industrial automation systems—relies on an efficient PCB assembly process. Yet, when discussing SMT and SMD, there’s often confusion about what each term actually means.

If you’ve spent time in electronics manufacturing, you’ve probably heard SMT and SMD used interchangeably. Some treat them as synonyms, while others assume they’re competing assembly methods—two entirely different ways to build a PCB. But that’s not right.

SMD refers to the components, while SMT refers to the process of placing and soldering them onto a PCB. The real comparison isn’t between SMT and SMD, but rather between SMT and through-hole technology (THT)—the two dominant methods of PCB assembly.

SMT vs. SMD vs. THT

While surface-mount technology (SMT), surface-mount devices (SMDs), and through-hole technology (THT) are often mentioned together, they serve distinct roles in the manufacturing process.

What is SMT?

Surface-mount technology (SMT) is the automated process that assembles electronic components onto a PCB without the need for through-holes. It is the industry standard for high-speed, high-density manufacturing, enabling the compact, lightweight devices we use daily.

By eliminating the need for drilled holes, SMT increases production efficiency, enhances performance, and reduces manufacturing costs.

What is SMD? 

Surface-mount devices (SMDs) are electronic components designed for SMT assembly. Unlike through-hole components with long leads that pass through drilled PCB holes, SMDs are mounted directly onto the board’s surface.

Common SMDs include:

• Resistors & Capacitors – Regulate signals and distribute power.
• Diodes & Transistors – Enable circuit switching and voltage regulation.
• Integrated Circuits (ICs) – The core of modern electronic devices.
• LEDs & Sensors – Essential for lighting, displays, and detection applications.

While SMT is the process, SMDs are the components that make it work.

What is THT? 

Unlike SMT, where surface mount packaging adheres components to the PCB surface, the through-hole process requires drilling holes to insert component leads, followed by manual or wave soldering.

Because of its mechanical strength and heat resistance, THT remains essential for applications where longevity and reliability take priority over size and speed.

SMT Assembly’s Effect on the Electronics Industry

Now that our terminology is in line, let’s consider how surface-mount technology has revolutionized modern electronics manufacturing. The shift from bulky, traditional through-hole components to compact, surface-mounted assemblies has enabled the creation of smaller, more powerful devices. 

Think about the wearable on your wrist, the IoT sensors automating industrial processes, or the smartphone in your pocket that gets thinner every year—none of these would be possible without surface-mount components.

Keep reading as we break down how SMT works, why it’s often superior for high-speed PCB production, and where through-hole technology still thrives. 

Whether you’re refining your manufacturing process or just looking to better understand the electronic devices you use daily, this article will give you the clarity you need.

How SMT Works: Our Process from Start to Finish

The smallest details make the difference between a PCB that works perfectly and one that fails in use. With over 30 years of experience in high-reliability electronics manufacturing, August Electronics has refined its SMT process to meet the stringent demands of industries like aerospace, medical, and industrial automation. 

Using state-of-the-art SMT technology, rigorous inspection protocols, and a highly skilled team, we build electronic systems that consistently exceed industry standards, ensuring every board meets the highest levels of precision and quality.

Here’s how our SMT process works:

Step 1: Solder Paste Application

A stencil applies solder paste to designated PCB areas. Precise application is critical because too much paste can cause bridging (unintended connections between SMT components), while too little can result in weak joints that compromise reliability.

We use advanced stencil printing technology and automated controls to ensure uniform paste distribution and minimize defects before components are placed.

Step 2: Solder Paste Inspection (SPI)

Many manufacturers rely solely on top-down 2D solder paste inspection (SPI) to speed up production, but this approach can overlook critical solder defects. 

We take quality a step further by utilizing both 2D and 3D SPI, ensuring a more precise and thorough inspection process. This allows us to detect issues like insufficient paste volume or misalignment before they compromise the PCB’s reliability.

Step 3: Component Placement

High-speed pick-and-place machines accurately position thousands of SMD components onto PCBs every minute. These machines operate with micron-level precision, ensuring each component is placed exactly where it needs to be. 

Our multi-head, high-speed placement systems handle a wide range of component sizes, from tiny 01005 resistors to complex Ball Grid Arrays (BGAs), ensuring efficiency without sacrificing accuracy.

Step 4: Reflow Soldering

The PCB moves through controlled reflow soldering ovens, where the solder paste melts and solidifies, permanently securing surface-mount components in place. The temperature profile is carefully managed through multiple heating zones to prevent thermal stress, ensuring a strong and reliable solder bond without damaging sensitive components.

Reflow profiles are optimized based on material specifications, minimizing warping and ensuring peak performance in high-reliability applications.

Step 5: Automated Optical Inspection (AOI) & X-Ray Inspection

AOI systems rapidly scan PCBs using high-resolution cameras and advanced algorithms to detect defects such as misaligned components, missing parts, solder bridges, and cold joints. 

This automated process significantly reduces human error and ensures consistent quality control across high-volume production runs.

Step 6: Functional Testing & Quality Control

Final testing ensures that every assembled PCB functions as intended. At August Electronics, we use:

• Dielectric Testing
• Functional Testing
• AQL (Acceptance Quality Limit) Inspections

Why SMT Has Become the Industry Standard

Surface-mount technology has largely replaced through-hole technology (THT) because it offers higher efficiency, better performance, and greater flexibility. 

1. Compact Designs & Higher Component Density

SMT allows for multi-layered PCB designs with smaller, more tightly packed components—ideal for wearables, IoT, and mobile devices.

2. Faster, Automated Production

Unlike THT, which requires manual soldering, SMT is almost entirely automated, reducing assembly time, labour costs, and production errors.

3. Improved Electrical Performance

Shorter electrical paths enhance signal integrity, reduce interference, and improve thermal efficiency.

4. Cost Savings & Material Efficiency

With smaller components, reduced drilling needs, and efficient automation, SMT lowers overall manufacturing costs.

At August Electronics, we operate four advanced SMT lines, ensuring efficiency, accuracy, and scalability in our manufacturing processes.

Where Through-Hole Technology Still Has a Place

Despite its advantages, SMT isn’t always the best choice. Through-hole technology (THT) remains essential in certain applications due to its superior mechanical strength and power-handling capabilities.

1. High-Stress Environments

THT components are soldered through the PCB, making them more resistant to mechanical stress and extreme temperatures. This is why industries like aerospace, automotive, and industrial machinery still use THT.

2. High-Power Applications

THT is better suited for high-power components, such as transformers and large capacitors, which require strong solder joints for heat dissipation and current handling.

3. Prototyping & Repairability

Through-hole components are easier to handle, remove, and replace, making them preferable for prototyping, testing, and repairable designs.

Manufacturers often use a hybrid approach, combining SMT for high-speed production with THT for high-power or stress-sensitive components.

Emerging Trends Shaping SMT and High-Speed PCB Manufacturing

As technology advances, SMT continues to evolve with innovations that improve miniaturization, automation, and efficiency. Some key trends include:

• 5G & High-Frequency Designs: Driving demand for lower signal interference and ultra-fast data transfer.
• AI-Driven Manufacturing: Machine learning for defect detection and process automation.
• Embedded Components & Advanced Packaging: Reducing board size and enhancing performance.
• Sustainable Manufacturing: SMT supports sustainability by minimizing material waste and resource consumption. Smaller components require fewer raw materials and less solder paste, contributing to reduced electronic waste. SMT assemblies’ high reliability and durability extend product lifespans, decreasing the frequency of replacements and landfill contributions.

Why August Electronics is Your Trusted Electronics Manufacturing Partner

SMT has revolutionized electronics manufacturing, making it possible to produce high-density, high-speed PCBs at scale. But achieving cost efficiency, reliability, and design optimization doesn’t come from simply knowing the difference between SMT and SMD—it comes from leveraging the right expertise, processes, and technology to get it right.

That’s why the right partner can make all the difference.

At August Electronics, we combine cutting-edge SMT capabilities with industry-leading quality control to deliver high-performance PCBs that meet the most demanding standards. From advanced 2D and 3D solder paste inspection (SPI) to X-ray validation for hidden joints and comprehensive functional testing, our state-of-the-art facility ensures unmatched accuracy and reliability in every build.

Whether manufacturing next-generation medical devices, high-speed telecom systems, industrial automation solutions, or mission-critical aerospace electronics, our expert team, automated precision, and end-to-end support will help you scale production, streamline your supply chain, and bring your products to market faster.
Contact us today to get started!