Through-Hole Vs Surface Mount Assembly

Through-Hole Vs Surface Mount Assembly

Many engineers that are starting out are often confused on the uses of the through-hole and Surface Mount Assembly (SMT) approaches to Printed Circuit Board (PCB) design.

If you are in that state of quagmire, we want you to know that you are not alone. We have taken the time to explain everything you need to know about the through-hole and surface mount assembly.

In this article, you will learn about the meaning of the through-hole and surface mount assembly, as well as their uses, differences and downsides.

Below are all the details you need to make an accurate comparison between the through-hole and surface mount assembly, as they pertain to PCB design.

Through-Hole Technology (THT)

Through-Hole Assembly

Before any other thing, we will like to mention that the Through-Hole technology is the older of other forms of designing Printed Circuit Boards (PCBs). For many decades, engineers relied on it for PCB design because of the reliability and excellent bond it creates on the circuit boards.

Ideally, the Through-Hole Technology involves using leads on the electrical components of a circuit board. When that is done, the next step is to insert the holes that must have been previously drilled on the circuit board. Afterward, the inserted holes will be drilled on the circuit board before soldering them to the pads positioned on the opposite side of the circuit board.

Advantages of Through-Hole Technology

The comparison of the Through-Hole Technology (THT) will not be complete if their advantages and differences are not stated.

So, we will first consider THT’s benefits and advantages. These are the factors that make it difficult for the Through-Hole Technology (THT) to go into obscurity even after the dominance of the Surface Mount Technology (SMT).

1. Easy Swapping for Excellent Prototyping

Most Printed Circuit Boards (PCBs) are prototyped so the possible outcome will be considered in time.

When it comes to that, it is imperative that the entire process is streamlined. And that is what makes the Through-Hole Technology (THT) ideal for PCB design because the easy of swapping it out makes prototyping and testing easier.

2. Ability of the PCB to Withstand Environmental Stress

Aside from designing the PCB to be ideal for different uses, considerations are also made for the exposure of the circuit board.

Environmental stress can cause the circuit board to wear out on time. However, the options for that are limited when using Through-Hole Technology for PCB design.

The leads used here are patterned to run through the circuit board. That way, the components will be less susceptible to environmental stress and other associated tear and wear.

Worthy of mention is that the use of the Through-Hole Technology for PCB design in many industries is because the circuit boards used there are not meant to be under any form of stress. That informs the reason why THT is ideal for manufacturing circuit boards for the aerospace and military industries.

Besides, the technology solidifies Printed Circuit Boards (PCBs) against high temperatures, extreme accelerations and collisions.

3. THT Components Provide Stronger Bonds

Engineers also prefer to use Through-Hole Technology because of the stronger bonds it provides on the circuit board.

Ideally, the use of THT for PCB design goes the extra mile to add additional resistance to PCB components that will be subjected to high heat coming from transformers and connectors.

4. Spend Less without Sacrificing on Quality

While you are looking for the best method to design your circuit board, you must also understand that price plays an important role too. To that end, it is safe to say that the Through-Hole Technology is ideal for any kind of Printed Circuit Board (PCB) design because it is less expensive when compared with the Surface Mount Technology.

Moreover, not all the PCB components are readily available as SMD packages and that is why you should consider THT for your PCB design.

In addition, you can also save money when using the Through-Hole Technology to design your circuit board because there may not be any need to generate a new solder stencil anytime the circuit board undergoes some changes.

5. Mechanical Easier Has Never Been this Easier

You tend to spend more money when designing a circuit board, especially when validating the board.

On the other hand, you can actually save some money if you are using the Through-Hole Technology for the design ahead of the validation.

The idea here is that Through-Hole Technology has a dedicated prototyping format that exposes potential mechanical shortcomings on the circuit board. That way, you will easily detect potential mechanical issues, such as twists and excessive warps.

Once these issues are detected during the validation process, the next step would be fix them or compensate for the lapses during the redesign process.

6. Through-Hole Technology Helps You Predict Delivery Timelines

Whether you have customers on the standby or you want to design the circuit board as fast as possible; you need to be sure of when it will be ready.

Most times, PCB manufacturers tend to give a delivery time, but might end up not meeting up with the same.

That problem has been solved with the Through-Hole Technology that provides you with an accurate timeline of when your circuit board will be ready for pickup and use.

The accuracy of the delivery timeline is because Through-Hole Technology follows up the development cycle from start to finish, as a way of simplifying the prototyping process and helping to put the project on track.

Disadvantages of Through-Hole Technology

Engineers started losing some interests in the use of the Through-Hole Technology because of some of the downsides.

While it is evident that THT has some downsides, that doesn’t entirely make it less effective than what the Surface Mount Technology (SMT) has to offer.

Here are some of the disadvantages and challenges you tend to come across when using Through-Hole Technology for your PCB design:

1. Assemblage Costs More Money

While you may not spend more money to buy the components for designing your circuit board using the Through-Hole Technology; you must also be prepared to spend more money than you budgeted when it is time to assemble the components.

The reason for that is not far-fetched from the fact that the assembly process for Through-Hole Technology is expensive because of the longer time and the rather complicated processes involved.

2. Through-Hole Technology Takes More Time

Second, you will realize that you tend to spend more time when designing your circuit board with Through-Hole Technology because the technology takes more time because of the manual process.

The first time-consuming factor is drilling holes on the board, as that takes more time when compared to the mounting of components as obtainable in Surface Mount Technology (SMT).

The second time-consuming factor is the soldering of both sides of the circuit board.

3. The Reliability of THT Circuit Boards are a Bit Low

Despite the manual design process that ought to give more room for precision, it is still evident that the reliability of the Through-Hole circuit boards is a bit low.

The reduced reliability of the boards is because Through-Hole Technology often uses hand-soldering techniques including selective and waves.

Those tend to reduce the reliability of the THT circuit boards, especially when compared to the reflow ovens that aren’t usually repeated on Surface Mount circuit boards.

4. Through-Hole Circuit Boards Have Limited Routing Areas

The availability of more routing areas on a circuit board could have provided more avenues for improving the aesthetics of the board.

That doesn’t appear to be the case with the Through-Hole circuit board because the drilled holes are passed through all the available layers on the circuit board.

That is the more reason why many engineers find it challenging to design multilayer boards with Through-Hole Technology because the routing areas are limited.

Surface Mount Technology (SMT)

Surface Mount Assembly

Surface Mount Technology (SMT) is the youngest of the PCB design generation in that it was later used to replace the former – the Through-Hole Technology.

This PCB design method seemed to be better in that it uses mounting of PCB components to replace the previous format of drilling holes, as tenable in the Through-Hole Technology (THT).

To that end, it is safe to say that the SMT format is simpler because all there is to do is to place or mount the PCB components directly onto the surface of the circuit board.

Advantages of Surface Mount Technology

Do you want to know some of the benefits of designing your Printed Circuit Boards (PCBs) using Surface Mount Technology (SMT)?

There are many reasons why SMT could be the best circuit board design technology. Below are some of the advantages:

1. SMT Provides Component Density and More Processing Power

PCB design started taking a different dimension a few decades ago. With the introduction of Surface Mount Technology (SMT), engineers now have more options to select from when it comes to PCB design.

Now, the first benefit and advantage of using SMT for your PCB design is that it provides you with a lower component density. That means that every circuit board component would be made to fit into smaller and lighter spaces.

2. SMT Components Do not Have Leads

Another advantage of designing your circuit boards with Surface Mount Technology (SMT) is that the components do not require leads.

The replacement of leads with the direct mounting of components on the PCB means that you would now have more routing areas to add more components as a way of bolstering your circuit board real estate.

3. SMT Lends Itself to Assembly Automation

Do you want to produce more circuit boards faster and at affordable rates? While you may not easily obtain that when using Through-Hole Technology; it can be easier when using Surface Mount Technology (SMT).

Because of the automation of PCB components assembly using SMT, you can now produce more circuit boards of higher volumes than you could have with the Through-Hole Technology.

4. SMT’s Strategic Placements Provide More Room for Powerful Circuit Boards

When designing your circuit boards with Surface Mount Technology (SMT), you are not only confident of not drilling holes on the board. You are also sure of more placement options.

Ideally, you can place your SMT components on both sides of your Printed Circuit Board (PCB). The dual placement provides more room for small and powerful circuit boards of high densities too.

5. SMT Circuit Boards are Highly Reliable

In a time like this that circuit boards are susceptible to damages, it is impressive to see that PCBs manufactured with Surface Mount Technology (SMT) are highly reliable.

The reliability of the circuit boards is partly because of the circuit board components can be placed up to 10 times faster than the Through-Hole variants. It is mainly because SMT circuit boards are designed using reflow ovens that are not only reliable, but also quick to assemble.

Finally, SMT circuit boards are tested and trusted to withstand different pressures, especially when they are used under vibrant conditions.

Disadvantages of Using Surface Mount Technology for PCB Design

There are some downsides that tend to make your SMT PPCB design less effective as expected.

Here are some of the potential bottlenecks engineers tend to experience when designing Printed Circuit Boards (PCBs) with Surface Mount Technology (SMT):

1. SMT Machinery Demands Huge Capital

While circuit boards designed with Surface Mount Technology (SMT) are cost-effective, the cost of acquiring the machinery may not be so.

Ideally, SMT machinery procurement requires more capital than what the Through-Hole machinery requires.

2. SMT Solder Joints Can Break Under the Influence of Constant Stress

One of the major reasons why engineers prefer using Through-Hole Technology (SMT) for circuit board design is because the leads provide additional strength to the circuit board.

On the contrary, the absence of leads on Surface Mount circuit boards tends to increase the board’s exposure to physical stress. In light of that, the solder joint of the SMT PCB could break from physical stress of the parts when used normally.

3. Some SMT Parts aren’t Available

If you are looking to design larger circuit board parts for high-power applications, it may not be tenable with SMT circuit boards.

That is because some of the SMT parts required for such applications aren’t readily available.


Through-Hole and Surface Mount technologies are the best of both worlds when it comes to circuit board design. You only need to consider the volume, the applications and your budget to make an informed decision.

And when you are ready to do that, Ray PCB is always ready to help you make an informed decision!


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