Through-Hole Versus Surface Mounting

By Gary Rothstein

In recent years, semiconductor packaging has advanced with an expanded demand for more extensive functionality, smaller size, and added value. A modern PCB assembly design has two central methods for mounting components onto a printed circuit board: Through-Hole versus Surface Mounting.

Through-hole components are mounted on a printed circuit board (PCB) by inserting their leads or terminals through holes in the board and then soldering them onto the opposite side. Surface mount components, on the other hand, are mounted directly onto the surface of the PCB without the need for through holes. They are soldered onto pads on the surface of the printed circuit board.

The main difference between through-hole and surface-mount components is how they are mounted and soldered onto the PCB. Through-hole components are usually much larger and have wire leads or terminals inserted through holes in the PCB. To ensure stability, they often require additional mechanical support, such as soldered pins or connectors.

Surface mount components, on the other hand, are smaller and more compact. They are typically made up of tiny chips or packages with solderable pads on the bottom. These components are soldered onto the pads on the PCB using various methods, such as reflow soldering or hand soldering with a soldering iron.

In terms of manufacturing and assembly processes, surface mount components are faster and more cost-effective to produce compared to through-hole components. They allow for higher component density on the PCB and can be automated for mass production. However, Through-hole components are often used for applications requiring higher mechanical stability or power requirements. They can also be easier to evaluate and replace.

Another difference is the availability and variety of components. Surface mount components have become more prevalent in recent years and are now more widely available. They also offer a more comprehensive range of sizes, packages, and technology options. Through-hole components, on the other hand, are still used, particularly in industries that require ruggedness and durability, such as automotive, aerospace, and industrial applications. Depending on the overall design, through-hole versus surface mounting decisions are often driven by the application still today.

Through-hole versus surface mounting example.
Example of SMT and Through-Hole parts on one PCB

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