Why Use Through-Hole Technology in PCB Design?

March 28, 2017 Alexsander Tamari

Close up of Through-Hole Components, very tiny protrusions

When it comes to technology, we never look back, always forward. Sometimes, though, it seems that the old technology just won't phase out. But is it really that simple? From the PCB design perspective, this blog will answer the question, why use through-hole mounting (THM) in printed circuit boards (PCB) when it seems surface mount technology (SMT) is the way to go?

Why use through-hole mounting (THM) in printed circuit boards (PCB) when it seems surface mount technology (SMT) is the way to go?  To start, let’s give a quick breakdown of each through-hole mounting and surface mount technology as it pertains to the PCB design process.

 

Through-Hole Components

Through-hole components come in one of two types of leads, radial and axial. Axial through-hole components run along the axis of symmetry of the component while radial components protrude in parallel from the same surface on a board.

 

Illustration showing the component side of the PCB design

Side View of a Through-Hole Component

 

 

Components of Surface Mount Technology

If you take a look at any modern PCB design, this is what you’ll see. Surface mount technology (SMT) is the most commonly used package technology today. These types of components have very small or no leads as their primary purpose is to be soldered directly on the surface of a PCB during the design process.

 

Components for surface mounting on PCB board

Surface Mount Devices
 

Pros and Cons of Through-hole vs. Surface Mount Technology

But if surface mount components are smaller, faster, and cheaper, then why use through-hole technology at all?! The answer depends on the use case for your PCB design. Yes, through-hole technology is old, big, and expensive, but there are some advantages.

 

Through-Hole Technology Pros and Cons

PRO

CON

Easier prototyping

Higher board cost due to drilling

Strong physical connections                           

Takes up more board real-estate

Heat tolerance

Assembly process is more involved        

Power handling capability

Slower speeds

 

 

Surface Mount Pros and Cons

PRO

CON

Small size → Denser boards

Weaker physical connections to the PCB

Fast speeds

Lower heat tolerance

Faster & cheaper assembly

Lower power handling capability

No drilling → Cheaper board fabrication        

DFM: tombstone, pop cornering, etc

 

 

 

When comparing the two PCB design technologies, it's easy to see why surface mount is the reigning champ. Surface mount devices (SMDs) are smaller, faster, and cheaper. This is especially important with IoT.

Technology leaders are driving towards a connected society and size does matter when it comes to PCB design. In the drive for ubiquitous computing, IoT or the “ambient intelligence” we all crave, the drive to make smaller and smaller components includes the very heart of the electronic devices, the circuit board.

Smaller components enable smaller boards, allowing us to fit PCBs in almost any form factor. Smaller sizes mean less to manufacture leading to cost reductions in the production process. Less expensive components will lead to cost savings to the end customer, which is always a plus.

High-speed designs are increasingly common and in demand, so SMDs are something we can’t substitute. Through-hole tech is great for prototyping and testing as you’re able to more easily swap out components on a PCB. Even before you make the circuit board, you can breadboard your PCB design.

 

 

PCB board prototype or breadboard using through-hole

Breadboard With Through-Hole Components
 

In addition to prototyping and testing, through-hole components have very strong physical bonds to the board as they are soldered from both the top and bottom of the board. Because of this, they are very durable, which is partly why they are used in military and aerospace. They also have a high environmental and power tolerance.

 

 

LED billboards powered by PCBs using through-hole technology

            Through-hole LEDs in outdoor signs            
 

 

You can find through-hole technology in all sorts of places. One example would be on LED lights in billboards or stadiums. Through-hole LEDs are extremely bright and durable, allowing them to handle the outside elements.

 

Through-hole components close up

Through-hole components in a power supply

 

Also, if you look at industrial machines and equipment you can find many through-hole circuit boards. Again, this is due to the harsh conditions, which could be environmental or something like having to deal with high power situations. Through-hole technology may be old and seem outdated, but it has a purpose and can be used for its physical endurance and strength in today’s connected world.

Curious to learn more? Visit our popular PCB design guidelines blog and learn from our experts. 

 

 

About the Author

Alexsander Tamari

Alexsander joined Altium as a Technical Marketing Engineer and brings years of engineering expertise to the team. His passion for electronics design combined with his practical business experience provides a unique perspective to the marketing team at Altium. Alexsander graduated from one of the top 20 universities in the world at UCSD where he earned a Bachelor’s degree in Electrical Engineering.

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