SMT vs THT Assembly – Which Is Right for Your PCB Design?
Choosing the right assembly method is one of the most important decisions in any PCB project. The two primary approaches – Surface Mount Technology (SMT) and Through-Hole Technology (THT) – both offer unique advantages, and understanding the differences helps ensure your board performs reliably and cost-effectively.
This guide explains how SMT and THT work, where each method excels, and how to choose the best option for your PCB assembly project.
What Is SMT Assembly?
SMT assembly is a highly automated process where components are mounted directly onto the surface of the PCB. This method allows for compact, lightweight, high-density board designs and is widely used in modern electronics.
How SMT Works
Solder paste is applied using a stencil.
Components are placed by automated pick-and-place machines.
The board passes through a reflow oven to create solder joints.
AOI or visual inspection verifies accuracy.
Benefits of SMT PCB Assembly
Supports fine-pitch and miniature components (0201, QFN, BGA).
Ideal for modern compact designs.
Faster assembly and lower labour costs.
Excellent for medium to high-volume production.
Typical Uses
Consumer electronics
IoT devices
Automotive electronics
High-density digital circuits
What Is THT Assembly?
Through-Hole Technology involves inserting component leads through holes drilled in the PCB and soldering them on the opposite side. THT is well-suited to mechanically strong, high-power or high-reliability assemblies.
How THT Works
Leads are inserted through the board manually or by machine.
Soldering is performed via wave soldering, selective soldering or manual soldering.
Joints are inspected for mechanical reliability.
Benefits of THT PCB Assembly
Stronger mechanical connections.
Excellent for components under stress or high currents.
More tolerant in harsh environments.
Easier prototyping for beginners.
Typical Uses
Power supplies
Industrial control systems
Aerospace and defence electronics
Connector-heavy boards
Should You Choose SMT or THT?
Most modern PCBs use a combination of both, known as mixed-technology assembly.
Here’s how to decide which method suits your design:
Choose SMT if you need:
Compact layouts
Miniature components
Fast or large-scale production
Lightweight assemblies
Choose THT if you need:
High mechanical strength
High-voltage or high-current paths
Large connectors, relays or transformers
Boards for harsh environments
Mixed-Technology PCB Assembly
Many projects require both SMT and THT. For example, you may design most of the board as SMT for space efficiency, while still relying on THT for connectors or larger components.
A skilled UK assembler like First Choice Assembly ensures both methods are seamlessly combined and soldered in the correct sequence.
Need Help Choosing the Right Assembly Method?
Our engineers can review your design and advise whether SMT, THT or a mixed approach is best for your project.
Explore our full PCB Assembly Services or get a fast quote today.
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