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20 May 2026
A Printed Circuit Board Assembly (PCBA) is a populated circuit board that includes the bare Printed Circuit Board (PCB) and the electronic components required for it to function. PCBAs are found in nearly every modern electronic device, from electric toothbrushes to fighter jet cockpits.
Transforming PCBs into PCBAs requires an assembly process. The two most common, tried-and-tested, and versatile assembly options for PCBs are Surface Mount Technology (SMT) and Through-Hole Technology (THT). Both options offer their own advantages, drawbacks, and best-case uses.
At J-TEQ, we use our industry expertise to help our clients find the most suitable solution for their project needs. This includes understanding the project requirements and deciding which assembly method will yield the best outcomes. What are the main differences in these assembly methods, though, and how does that guide our choices?
In this article, we will take a closer look at through-hole vs surface mount technology, their differences, applications, and more.
Through-hole technology (THT) is a popular method of mounting electronic components onto a bare PCB. It involves inserting component leads into pre-drilled holes in the board, then soldering them to pads on the opposite side. This creates a strong electrical and mechanical connection.
THT was one of the first methods of assembling PCBs, dating back to the mid-20th century, and is still used today for a wide range of projects. At J-TEQ, we use THT as a reliable option for assemblies that need to be durable, thermally resilient, and easy to service or maintain.
Through-hole components use long metal leads or pins that pass through the drilled holes found on prepared PCBs. Some commonly used components in THT include:
THT is typically used for environments that require PCBAs to be mechanically robust and reliable. Common applications that we have used for THT include:
As you can probably surmise from the applications of THT, one of its biggest strengths is its mechanical durability. As the component leads pass through the PCB before being soldered to the other side of the board, the connection is very secure. Our technicians use THT when parts may be subject to physical stress, such as connectors, terminals, and larger components.
Another key strength of THT is its ability to handle high-power and high-voltage applications. As THT components are typically larger than surface-mount alternatives, they are often better suited to applications involving higher current, heat, or electrical stress. These larger components also make THT quite easy to inspect, repair, and test, making them useful for prototyping and low-volume production.
Although ideal for some scenarios, THT has limitations. The components' size takes up a lot of board space, so routing options are limited. THT assembly is also generally slower and more labour-intensive than SMT, as holes must be drilled and components inserted. Soldering will also need to be completed manually, by wave soldering or selective soldering.
As working with THT components is quite slow, it isn't suited to high-density or highly automated environments. For modern compact electronics, THT is usually used selectively rather than as the primary assembly method.
At J-TEQ, we ensure we spend time understanding a project's requirements and limitations, allowing us to assess whether THT is the right option for the project or whether an alternative assembly solution might be right.
Surface mount technology (SMT) became widely adopted in the 1980s as manufacturers looked for faster, more compact, and more automated ways to populate PCBs. Instead of inserting component leads through drilled holes, surface-mount components are placed directly onto copper pads on the board's surface.
These components may use small leads, flat terminals, contacts, or solder balls, depending on the package type. As they can be smaller than their THT counterparts, SMT boards allow us to accommodate high component density. Our team at J-TEQ uses these more discrete components to support smaller devices, better performance, and enhanced functionality.
The surface mount assembly process also allows for much greater automation. Surface-mount devices are mounted directly onto boards using pick-and-place machines, which supports high-speed production. THT typically relies on manual (or partially automated) assembly, whereas SMT supports faster production with less human involvement. So, we may choose this approach if high-volume, high-speed production is core to your project.
The boards used for both THT and SMT are similar, but SMT boards have slightly different surface-mount pads without holes drilled through them. Another key difference between these two assembly processes is the addition of solder paste onto the pads for SMT, which fundamentally changes how components are mounted.
Surface-mount components are placed directly onto copper pads on the PCB. They are typically designed with small terminals, flat contacts, or short leads instead of the long pins found in THT. Some commonly used components in SMT include:
SMT components are most commonly found in consumer and commercial devices that require small size, high speed, and low production costs. This makes them ideal for mass-market production of devices such as:
It's hard to understate how significant the adoption of SMT has been for technological innovation. The strengths this assembly process provides have made it the most commonly used technique by electronic manufacturers today. By enabling a more automated assembly process, production is faster, more consistent, and more reliable.
SMT components are also smaller, supporting greater component density on PCBs and enhanced functionality for PCBAs. This reduced weight makes SMT ideal for smaller devices and portability. Components can also be mounted on both sides of the PCB with this process, adding even more flexibility to designs. The small size means shorter connections, which reduces signal delay and improves performance at high frequencies.
Efficient automation, coupled with lower material costs, makes SMT assembly generally more cost-effective than THT. We consider all of these strengths at J-TEQ to devise the right solution for your project needs.
Although SMT was a true revolution in PCB assembly, there is a good reason that THT and mixed-technology assemblies are also in use today. SMT requires high-precision equipment, which is a big investment. This high initial cost makes SMT less suited for low-volume runs.
SMT's small component sizes are useful in some applications, but they aren't ideal for prototyping or manual assembly due to their complexity. It also makes inspections, repairs, and replacements much more involved due to the smaller space in the board layouts. Smaller pitch sizes also make bridging a common issue in SMT assembly that can lead to shorts.
SMT connections are generally less mechanically robust than THT joints. Due to this, additional design consideration may be needed for components exposed to vibration, repeated handling, thermal stress, or mechanical strain. Our experts at J-TEQ will consider your ideal outcomes to decide which option works best. Not all projects benefit from SMT, or SMT alone, which is why having electrical engineering expertise on your side is very helpful.
Choosing THT or SMT for your PCB layout will largely depend on component types, product requirements, and manufacturing priorities. With years of industry experience, our team at J-TEQ will assess your project needs before deciding which option suits your desired outcome.
THT is ideally suited for projects where strength and durability are a top consideration. THT has a much stronger mechanical bond because the component leads pass through the board. We typically choose THT for components that will likely experience physical stress or harsh environments.
We tend to use SMT for projects where space, speed, and efficiency are top priorities. Due to the direct-mount design of SMT boards, they are perfect for smaller, lighter designs. It also supports better automation and high-volume manufacturing, which is why it's often used for modern electronics.
In some cases, the best option is to adopt a mixed-technology assembly that brings together THT and SMT. This approach provides the best of both worlds: SMT components are used for high-density circuitry, and THT components are used for stability and reliability for specific parts of the PCB.
As we have covered, SMT and THT have their own benefits and drawbacks. A mixed-technology assembly can incorporate the best elements of both methods. However, it can also introduce additional complexity. For example, mixed-technology assemblies can be more complex and costly than using a single assembly method, as they may require additional process steps, tooling, or inspection.
Most of our clients rely on our expertise to guide projects to find the best assembly path for their needs. We take into account the key details that you need to cover and devise the best solution for you.
To give you a clear picture of how these different PCB assembly methods stack up, we have compiled a comparison table below. It summarises the main differences between THT, SMT, and mixed-technology assembly to show where each approach is most useful.
| Assembly type | Through-hole technology (THT) | Surface mount technology (SMT) | Mixed-technology assembly |
| How it works | Component leads run through pre-drilled holes in the PCB and are soldered onto pads on the opposite side. This is usually done manually or semi-automatically. | Components are placed directly onto copper pads on the PCB surface. It is usually soldered using solder paste via automated processes. | A combination of SMT and THT on the same PCB. This approach uses each method where it offers the most value. |
| Key strengths | Strong mechanical bondDurable and reliableEasier to inspect, test, and repairSuitable for higher current, heat, and electrical stress | Compact and lightweightSupports high component densitySuitable for high-speed automated productionUsually cost-effective at scaleImproves high-frequency performance | Balances compact design with mechanical strengthAllows SMT for dense circuitry and THT for larger or high-stress partsOffers greater design flexibility |
| Key weaknesses | Takes up more board spaceSlower and more labour-intensiveLess suited to high-density layouts or automated production | Less mechanically robust than THTHarder to inspect, repair, and replace manuallyLess suited to low-volume or prototype runsRequires high-precision equipment | More complex than using a single assembly methodMay require additional process steps, tooling, soldering methods, or inspection |
| Best suited for | Projects where strength, durability, serviceability, or resilience matter (connectors, terminals, larger components, harsh environments) | Smaller, lighter, and more complex devices where space, speed, efficiency, and high-volume production are priorities. | Projects that need both high-density electronics and durable, reliable connections for specific components. |
Choosing between THT, SMT, or a mixed-technology PCB solution is not always straightforward. You often need to consider a variety of factors, ranging from product requirements and performance expectations to production volume and budget.
Our team at J-TEQ is here to help your project thrive by assessing your needs and identifying the most suitable PCB assembly method for your application. Whether your project needs the strength and reliability of THT, the compact efficiency of SMT, or a combination of both, our team of electronics manufacturing experts will identify what works best for you.
We excel in both SMT and THT assembly, as well as a host of other useful services, including prototyping, PCB testing, and value engineering. Regardless of the scope, scale, or nuance of your project, J-TEQ can provide the expertise required to help you reach the right PCB solution.
Let J-TEQ support your next project with electronic manufacturing services built around your needs and standards. Find out more by reaching out to one of our team members today.
