Surface Mount Components vs Through Hole

PCB with surface mount and through hole components

Paper or plastic packaging? Red or white wine? Michael or LeBron? Tabletop or video games? These are just a few of the perplexing questions in life that many people struggle with. As PCB designers, we have our own bewildering issue. Surface mount components or through hole.

Although, surface mount parts have been around since the 1960s, through hole components dominated the market until the 1990s. Today, most components are available in surface mount technology SMT) packaging , especially integrated circuits. This prevalence, coupled with the distinct advantages of opting for each type, make it imperative that engineers and PCB designers know when and how to choose between surface mount components vs through hole.

Comparison: Surface Mount Components vs Through Hole

As the demand for smaller electronics continues to grow, the utilization of surface mount components instead of through hole components increases. Smaller and lighter components is a one of the major assets that surface mount components bring to a design. However, there are benefits unique to through hole parts, as well. The advantages of both component types are listed below.

SURFACE MOUNT COMPONENTS VS THROUGH HOLE COMPONENTS
Surface Mount Advantages	Through Hole Advantages
Parts can be mounted on the top and bottom surfaces, enabling double-sided PCB manufacturing.	Mounting supports larger and stronger parts. For example, power supplies
Components are smaller and lighter.	More secure connections.
Allow for greater component density.	More resilient to physical stress and strain.
Less drill holes needed.	Best for when part may require regular interfacing. For example, switches and connectors.
Minimize or eliminate the need for manual intervention during manufacturing.	More reliable in hazardous environment implementations.
Support increased automation for placement and soldering.	Easier to manually solder. For example, when rework is required.
Better electrical performance.	Can be used for higher power applications.
Lower unit cost.	Some devices are only available as through hole components.

It is obvious from the table above that comparing surface mount components vs through hole is not a simple apples to apples evaluation. In fact, each component type has some distinct benefits that make it the logical, if not only, option for some situations. Therefore, the question is not which is better than the other, but when is the best time to choose which component type?

Surface Mount or Through Hole? How to Choose

Part selections are the most important decisions that designers make during the PCBA design process. Typically, the component datasheet is the primary source of determinant qualitative and quantitative information, such as common applications and electrical characteristics, respectively. Yet, the fact that your component choices impact all three aspects of the design⇒build⇒test (DBT) process, necessitate that design for manufacturing (DFM), design for assembly (DFA), and design for testing (DFT)–if necessary–are considered.

For guidance In choosing whether to use surface mount components vs through hole that best satisfies your circuit’s functionality and performance objectives, while also adhering to manufacturing requirements it is helpful to answer the following questions.

QUESTIONS	Surface Mount	Through Hole
Is your design a double-sided PCB?	✓
Is high component density required for your design?	✓
Is electrical performance the priority for your design (e.g. high-speed or high frequency signal processing)?	✓
Does your design include heavy parts (e.g. power supplies, transformers)?		✓
Will your board be subjected to hazards like vibration or high temperatures?		✓
Does your design include components that are only available as through hole?		✓

The questions above will help you choose between surface mount technology (SMT) and through hole technology (THT) as a component selection strategy. The chief advantages of opting for a broad strategy is that it simplifies the assembly process for your CM, as surface mount components and through hole components typically involve different soldering processes. For SMT, reflow is the standard soldering method. For THT, wave soldering is most often implemented.

In some cases, for example when parts are not available in one of the surface mount device (SMD) packages, both SMT and THT must be utilized. Therefore, it is necessary to choose between surface mount components vs through hole for individual parts. Doing so will enable you to optimize your design for the most efficient PCB development process.

Optimizing Your SMT and/or THT PCB Design

Choosing the wrong components is one of the most costly errors you can make with your design. Replacing components almost always leads to the need for redesign, respin and retesting. Therefore, it is imperative to optimize your component selection the first time, for an efficient and cost-effective development process. Accomplishing this is best achieved by following guidelines, as listed below.

Best Surface Mount and/or Through Hole PCB Design Guidelines

Understand the benefits and advantages of choosing surface mount and through hole components on the building of your boards.
Acquire and follow your CM’s manufacturing rules, especially design for assembly directives.
Only source components from a reliable resource, that includes supply chain data.
Make sure that your SMT and/or THT component models and data are accurate.

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