Through-Hole vs Surface Mount Components: Pros, Cons, PCB Design and Assembly Trade-Offs

When designing a PCB, engineers should choose between through-hole components and surface mount devices (SMD). This choice directly impacts board size, assembly cost, mechanical reliability, and electrical performance. Understanding the key differences in Through-Hole vs SMD helps designers optimize both manufacturability and long-term reliability.

In modern PCB manufacturing, both technologies are widely used. Many designs adopt a mixed-technology approach, combining SMDs for high-density circuits with through-hole components for connectors or high-power parts—an approach fully supported by professional PCB assembly service such as JLCPCB.

Through-Hole vs Surface Mount Components: Key Differences Overview

Through-Hole Components

Through-hole components are named after the holes that are drilled into a printed circuit board (PCB) to accommodate the leads of the component establishing the connection of the components to the circuit copper traces. These components have lead wires that pass through the holes in the PCB, and they are then soldered on the opposite side.

Advantages of Through-Hole Components

Durability: Through-hole components have a higher level of durability as they are more resistant to vibration and shock due to their leads connection that takes large surface on the board. This makes them ideal for applications that require ruggedness, such as in aerospace industries.

Reliability: Through-hole components are easier to troubleshoot and replace when they fail. This is because their leads are easily accessible and can be soldered by hand without the need for special equipment and the minimum electronics assembly knowledge will make you able to easily solder most of the possible components.

Easier to work with: Through-hole components are easier to handle and place on the PCB, especially for beginners. They also provide a stronger mechanical connection, which means they can withstand higher levels of stress and strain.

Disadvantages of Through-Hole Components

Time-consuming: Through-hole components require more time to install as they need to be manually inserted into the PCB holes and soldered.

Larger size: Through-hole components are larger in size than their surface mount counterparts. This can be an issue for miniaturization in designs where size and space are a concern.

Cost: Through-hole components are generally more expensive than surface mount components. This is because they require more material and are more labor-intensive to install.

Surface Mount Components

Surface mount components (SMD) are designed to be mounted directly onto the surface of the PCB without the need for holes. This makes them more compact and enables them to be placed closer together, allowing for higher circuit densities.

Advantages of Surface Mount Components

Size: Surface mount components are smaller in size, making them ideal for applications where space is limited.

Speed: Surface mount components can be installed faster than through-hole components as they can be soldered using automated machines.

Cost-effective: Surface mount components are generally cheaper than through-hole components, as they require fewer materials and less labor to install.

Disadvantages of Surface Mount Components

Durability: Surface mount components are more susceptible to vibration and shock, making them less suitable for rugged applications.

Difficult to troubleshoot: Surface mount components are difficult to troubleshoot and replace, as their small size and close proximity to each other make them hard to access.

Solder joint reliability: Solder joint reliability is a potential issue with surface mount components, especially if the PCB is subject to thermal cycling or other forms of stress.

Through-Hole vs Surface Mount: Design Considerations

When choosing between through-hole and surface mount components, engineers must evaluate more than package type. Key design considerations include board size, signal integrity, mechanical reliability, and thermal performance.

Board Size and Layer Count

Surface mount components enable higher component density and smaller PCB footprints, making them ideal for compact, multi-layer designs. Through-hole components require drilled holes and larger pad spacing, which increases board area and can limit routing flexibility—especially on high-density or multi-layer PCBs.

Signal Integrity

SMDs typically offer shorter lead lengths and lower parasitic inductance and capacitance, resulting in better high-frequency and high-speed signal performance. Through-hole components, with longer leads passing through the PCB, may introduce additional parasitics that can affect signal integrity in high-speed or RF designs.

Mechanical Stress and Reliability

Through-hole components provide strong mechanical anchoring due to leads passing through the PCB, making them more resistant to vibration, shock, and mechanical stress. This makes them suitable for connectors, transformers, and power components. Surface mount components rely solely on solder joints for mechanical support and may require additional reinforcement in harsh environments.

Thermal Performance

Through-hole leads can help dissipate heat through the PCB, which is beneficial for high-power components. However, modern SMD packages with thermal pads and vias can achieve excellent heat dissipation when properly designed. Thermal performance ultimately depends on PCB layout, copper area, and thermal management strategy rather than assembly method alone.

Through-Hole vs SMD in PCB Assembly

From a manufacturing perspective, through-hole and surface mount technologies differ significantly in terms of assembly process, automation level, cost structure, and production scalability. Understanding these differences helps engineers choose the most efficient assembly method for their project.

Assembly Process Differences

Through-hole assembly requires component leads to be inserted into drilled PCB holes, followed by soldering using wave soldering, selective soldering, or manual soldering. This process is generally slower and involves additional mechanical steps such as drilling and lead trimming.

Surface mount assembly places components directly onto solder paste–printed pads and solders them using reflow soldering. The entire SMT process—solder paste printing, pick-and-place, and reflow—is highly automated and optimized for speed and repeatability.

Automation and Production Efficiency

SMT is inherently suited for high-speed automated production. Modern pick-and-place machines can mount tens of thousands of components per hour with high placement accuracy, making SMD assembly ideal for mass production and high-density designs.

Through-hole assembly is more difficult to fully automate, especially for mixed or low-volume production. While wave and selective soldering can improve efficiency, through-hole processes still involve more manual intervention compared to SMT.

Cost and Scalability

Surface mount assembly typically offers lower assembly costs at scale due to reduced labor, smaller PCB size, and faster throughput. Component packaging and panelization further optimize SMT for large-volume manufacturing.

Through-hole assembly tends to have higher per-unit costs, particularly for large production runs, due to longer assembly time and increased material usage. However, for low-volume builds or mechanically critical components, through-hole assembly remains cost-effective and practical.

Further read: SMT vs Through Hole: Which PCB Assembly is Most Cost-Effective?

Mixed-Technology PCB Assembly

In many real-world designs, through-hole and SMD components coexist on the same PCB. Mixed-technology assembly typically involves SMT reflow soldering first, followed by through-hole wave or selective soldering. This approach combines the compactness of SMDs with the mechanical strength of through-hole components.

Professional PCB assembly services support single-sided, double-sided, and mixed SMT + through-hole assembly to meet diverse design and reliability requirements.

Also Read:

1. Surface Mount vs Through Hole: Technical PCB Guide

2. SMT Assembly Process Explained and Equipment Used

Conclusion

Both through-hole and surface mount components have their own advantages and disadvantages when it comes to circuit board design. The choice between the two depends on the specific requirements of the application, such as the level of durability, size, cost, and ease of installation. Therefore, it is essential to consider all the factors before selecting the components for the design. By doing so, the designer can ensure that the circuit board meets the necessary requirements and functions optimally.