SMD assembly vs. THT mounting: which technology suits your project?

In electronics manufacturing, developers and buyers regularly face the same question: SMD or THT, which process suits the project? SMD (surface mount device) refers to mounting components directly on the surface of a circuit board. THT (through-hole technology), on the other hand, inserts the components through holes and solders them on the back. Both processes have clear strengths. The right choice depends on factors such as quantity, mechanical load and the requirements for the circuit board design. This article explains which solution makes sense when, and when a combination of both techniques offers the best compromise. As an experienced partner for assembly, we at SICATRON support you from concept to series-ready production.

Table of contents

1. Key points at a glance
2. What distinguishes the two processes?
3. When is the SMD process worthwhile?
4. When is THT assembly the better choice?
5. Combined assembly as a solution
6. FAQ
7. Conclusion

Key points at a glance

• SMD places components on the circuit board surface and enables a high packing density with minimal space requirements.
• THT inserts components through holes in the board and thus achieves superior mechanical stability.
• The SMT process is particularly suitable for automated series production with miniaturised electronic PCB assemblies.
• Hybrid PCBA designs deliberately combine both processes and so use their respective strengths.
• The choice of process has a considerable influence on circuit board design, manufacturing process and overall costs.
• Through-hole remains indispensable in modern electronics manufacturing, for example for rugged connectors.

What distinguishes the two processes?

The two dominant circuit board assembly technologies differ fundamentally in their mounting method. In SMD assembly, electronic components are placed directly on prepared solder pads on the board. The solder paste is applied using a stencil, the components are positioned automatically and soldered in the reflow oven. The SMT process can be fully automated and achieves high production speeds.

In the through-hole process, by contrast, components with long lead wires are inserted through drilled holes in the circuit board and fixed on the back by wave soldering. This anchors the components securely in the board and creates a particularly resilient connection.

Key differences at a glance:

• Placement: SMD assembly on the surface of the circuit board, through-hole through drilled holes
• Automation: SMT fully automatable; the through-hole process partly requires manual steps
• Size: SMD components are considerably smaller than through-hole components.
• Mechanical stability: THT-mounted components are considerably more resilient thanks to their anchoring.

When is the SMD process worthwhile?

The SMD process is the preferred choice when miniaturisation and production efficiency are what count. In mass production, for example for industrial control technology, communications technology or compact devices, SMT enables fast and cost-efficient manufacturing. The high packing density makes the process the standard in electronics.

Typical advantages of the SMD process:

• Low weight: miniaturised components noticeably reduce the overall weight of the assembly.
• Automation: a fully automated process lowers error rates and unit costs.
• Integration density: space-saving components enable a high density on the PCB.
• Cost efficiency: large PCBA quantities benefit from the high placement speed.

Typical areas of application for the SMD process are automotive electronics, industrial automation and compact PCBA solutions for embedded systems.

When is THT assembly the better choice?

Although SMT is widespread, the through-hole process has its firm place in modern electronics manufacturing. The decisive factor is above all mechanical stability: components exposed to strong vibration, tensile or compressive forces, such as connectors, transformers or power semiconductors, benefit considerably from being anchored through the board. With through-hole mounting, the physical connection is simply more robust.

The process also offers clear advantages in prototype development: components are easier to replace, adapt and access for repairs or manual rework. Safety-critical applications in industrial automation and medical technology also rely on the process, where durability and the mechanical testability of the board assembly come first.

Combined assembly as a solution

In industrial practice, SMD and THT are frequently combined on a single circuit board. SMT components handle the compact signal processing, while THT is used where mechanical strength or high current-carrying capacity is required, for example for connectors or power semiconductors. This hybrid assembly makes it possible to combine the strengths of both processes in a single assembly.

Typical application scenarios for combined circuit board assembly are found in:

• Power electronics: power semiconductors as through-hole components, control logic as SMD components
• Industrial controls: rugged interfaces via THT components, compact logic level via SMT
• Medical technology: high reliability through through-hole components, miniaturised sensors via SMD components
• Automation technology: mixed assembly for maximum functional density on the PCB

Such hybrid solutions require careful planning and an experienced manufacturing partner who masters both technologies reliably.

FAQ

Which technology is more cost-effective for small quantities?

For small quantities, the through-hole process is often more economical, as there is no set-up effort for SMT placement lines and no elaborate stencils or machine programs are needed. Manual production offers more flexibility here. Above a certain series size, the cost ratio reverses: the high degree of automation of the SMD process significantly lowers unit costs.

How does the choice of assembly technique affect circuit board design?

The chosen method has a considerable influence on the PCB layout. The SMT process requires precise solder pads and clearances for placement machines but allows a much higher integration density. The through-hole process requires drilled holes, solder eyes and sufficient spacing. Both processes place different demands on layer structure and thermal management.

Is THT still up to date in modern electronics manufacturing?

Yes, the process remains indispensable. Especially where mechanical strength, easy replaceability and high current-carrying capacity are required, THT is still the more reliable choice. In safety-critical applications such as medical technology or industrial automation, developers also value the easy testability and reworkability of THT connections.

Conclusion

The decision between the two processes always depends on the specific application. The SMD process impresses in automated series production with miniaturisation and cost efficiency. THT scores where mechanical stress, durability or easy maintenance are the priority. For many industrial applications, the combined technique offers the best compromise.

Our recommendation: analyse your requirements early, ideally in the development phase, and choose the process specifically according to quantity, stress and design goals. As an experienced system supplier, we support you from concept to the series-ready electronic assembly: precise, on schedule and “Made in Germany”.