Surface Mount vs Through-Hole: Pros & Cons

Surface Mount (SMT) and Through-Hole Technology (THT) are the two fundamental types of constituents utilized in printed circuit boards (PCBs). Surface Mount is used more frequently than Through Hole since it is more reliable and less expensive.

 

Surface Mount (SMT) and Through-Hole Technology (THT) are the two fundamental types of constituents utilized in printed circuit boards (PCBs). SMT involves mounting components directly on the surface of the PCB, while THT involves inserting components through holes in the board. Surface Mount is used more frequently than Through Hole since it is more reliable and less expensive. Nevertheless, Through Hole Technology provides distinct advantages that ensure its continued relevance for the conceivable future.

 

Pros and Cons Side by Side

 

Here are the main pros and cons of Surface Mount and Through Hole Technology:

 

Pros  

- SMT saves space, enabling smaller, lighter, and faster devices.  

- Surface Mount techniques offer cost savings, resulting in lower unit prices.  

- SMT provides higher manufacturing capacity than Through Hole.  

- SMT assembly is automated through process automation.  

- Through Hole Technology can better withstand environmental stress.  

- THT creates stronger bonds between components.  

 

Cons  

- Surface Mount Technology requires a higher level of design, production, skill, and technological innovation for implementation.

- SMT is challenging for visual inspection.  

- Through Hole Technology requires multiple holes on the board.  

- Through Hole has a longer production time than Surface Mount.

 

Types of PCB Assemblers  

 

There are various methods for Printed Circuit Board assembly, each differing in its ability to handle board complexities and perform specific construction and configuration techniques. The most common types are:

 

- Surface Mount Assembly: This process begins with loading the components into the pick-and-place machine’s feeders, followed by programming the required functionalities.  

- Plated Through Hole Technology: This method involves using holes that pass through the board, with most PCB assemblers employing in-circuit testing.  

- Electro-Mechanical Assembly: This method utilizes electromechanical equipment for assembling electronics onto PCBs.

 

 

Advantages & Disadvantages of SMT  

 

Advantages of SMT:  

- Improved manufacturing efficiency.  

- Greater design flexibility.  

- Enhanced performance of electronic components.  

- More compact electronic devices.  

- EMC-compliant design.  

- Automatic correction during auto-placement.  

- Reduced overall cost.  

- Consistent performance under shaking conditions.  

- Minimized waste.  

- Faster lead time.  

 

Disadvantages of SMT:  

- Issues under extreme conditions.  

- Poor resistance to thermal and environmental stress.  

- Not ideal for small circuit testing.  

- Difficult to inspect.  

- Components are more prone to damage.  

- Limited power availability.  

- More expensive for small batch development.  

 

Components on SMT-fabricated PCBs perform well under shaking and vibrational conditions. The absence of holes in SMT leads to significant cost savings, minimal waste, and faster lead times. The quicker component configuration, which is 10 times faster than THM, is made possible by the reliable soldering method using reflow ovens.  

 

However, issues may arise when SMT is the sole technique used for assembling PCB components subjected to extreme mechanical, environmental, or thermal stress. SMT components are also not ideal for small circuit prototyping or testing. Combining SMT with THM can offer the benefits of both methods to address these challenges.

 

What is Through Hole Technology (THT)?  

 

Through Hole mounting involves inserting component leads into drilled holes in a bare PCB. Before the rise of SMT in the 1980s, through-hole technology was the industry-standard method. While Surface Mount is more efficient and cost-effective, leading some to believe THT would become obsolete,  

 

Through Hole technology remains valuable, offering numerous benefits and specialized applications. Its greatest advantage is durability, with annular rings now providing a strong, reliable connection.

 

Differences Between Axial and Radial Leads  

 

Axial and radial leads are two types of THT components. Axial lead components have wires attached to both the front and back of the component, while radial components have leads on one side.  

 

Radial leads are ideal for densely packed boards as they occupy less space compared to axial leads, which fit closely against the board.

 

Advantages & Disadvantages of THT  

 

THT provides superior mechanical connections compared to SMT, making it ideal for components subject to mechanical stress, such as connectors and transformers. The wider spacing between holes makes manual soldering easier, and THT components are easily interchangeable, making them suitable for prototypes and testing.  

 

THT components are well-suited for durable products requiring robust interlayer connections. These connections allow components to withstand more environmental stress than SMT components, which are only held in place by solder on the surface.  

 

As a result, THT is commonly used in military and aerospace applications, where components face intense thrust, vibrations, or high heat.  

 

However, THT requires drilling holes in the bare PCB, which is time-consuming and costly. It also limits the available configuration area on multi-layer boards, as the drilled holes must pass through all layers. Additionally, THT’s component configuration density is much lower than that of SMT, making it more expensive for most applications.  

 

THT also requires wave, selective, or manual soldering methods, which are less efficient and reliable than SMT’s reflow ovens. Notably, THT requires soldering on both sides of the board, whereas SMT only requires soldering on one side.

 

SMT vs Through Hole: Cost Difference  

 

SMT, unlike THT, does not require manual drilling of holes in a PCB. A small PCB with fewer holes and layers will be less expensive. Additionally, pick-and-place systems accelerate component placement, and automatic reflow ovens handle reflow soldering, resulting in cost savings for SMT compared to THT.

 

While manufacturers can speed up THT configuration for mass production, they often rely on manual configuration due to component volume. Moreover, THT requires costly manual soldering to adequately cover high-density components. Since SMT offers greater automation flexibility, board prices decrease for bulk purchases.

 

SMT vs Through Hole: Differences in Assembly  

 

The main difference between SMT and THT assembly is that most SMT processes are automated, significantly reducing assembly time. With SMT manufacturing, shipments can be processed faster compared to THT, which requires setting up auto-insertion machinery for various THT components.

 

Although SMT can shorten component placement and board processing times, there are situations where THT is the better option, such as when the board design includes large or robust components that require extensive support.

 

Through Hole vs Surface Mount – What Is the Best Method for You?  

 

Choosing the right configuration method for your board can be challenging. While over 90% of today’s PCBs use surface mount technology, which is generally more efficient and cost-effective than through-hole technology, the best option depends on your specific needs. Surface mounting offers a lightweight design and allows for higher component density.