Through-Hole Assembly Vs Surface Mounting

Printed circuit boards (PCB) have become an essential part of the electronics industry as they are used to house and connect electrical components in lots of devices.

There are a variety of different electronic manufacturing solutions for these PCBs. Two of the most basic methods include Surface Mounting and Through-Hole assembly.

But what are the differences between these two methods and how do they work?

In the guide below, we’re going to take a look at Through-Hole assembly and Surface Mounting in more detail, comparing the two and looking at the pros and cons of each.

Read on to find out more.

What is the Through-Hole assembly method?

The Through-Hole assembly method is a very distinct technique. In this method, Pin-Through-Hole (PTH) component leads, both axial and radial, are inserted into drilled holes in the printed circuit board. The leads are then soldered onto the pads on the opposite side, this can be done by a machine or completed by hand depending on the size of the company.

Through-Hole assembly was the industry standard back in the 1980s and predated the Surface Mounting method. There are a number of pros and cons to choosing this assembly technique, and the benefits include:

  • Through-Hole Technology (THT) is more durable than other methods, including Surface Mounting
  • By soldering to the other side of the board, it creates stronger bonds between the components
  • This also means that it can withstand more environmental stress than other boards
  • These are easier to inspect after assembly

However, there are a few downsides to this method and these include:

  • Having a longer production time when compared to Surface Mount Technology (SMT)
  • It is also more expensive and therefore less cost efficient
  • It requires multiple holes to be drilled into the PCB

What is the Surface Mounting method?

Surface Mount assembly gained popularity in the 1980s and has since become prevalent in most electronic goods and gadgets. This method works by attaching the components directly to the PCB with solder; there is no need to drill any holes.

This assembly method is typically carried out by a machine, and as the components are smaller, they can be directly fitted to both sides of the board. Again, this has some unique benefits when compared to THT and the biggest pros of this technique include:

  • Enhanced PCB performance and reliability
  • Lower handling and production costs, leading to lower prices per unit
  • No need to drill holes into the boards, making them stronger
  • The SMT assembly process is automated and can therefore manufacture larger quantities in less time
  • Because the components can be fitted to either side, it’s possible to make more powerful and compact boards

But as with THT, there are some downsides to using this method and these are:

  • Surface Mounting requires a higher level of skills and technical innovation for assembly
  • It also requires more attention during the design and production stage
  • SMT assembly makes it harder to inspect the boards visually, automated testing is often required to make it possible

The differences between the two methods

So, in a nutshell, the key difference between these two methods is that THT requires drilling holes and the leads are soldered to the underside of the board. Whereas, in SMT components are attached directly to both sides of the PCB.

Thanks to the lack of holes in SMT, it can be quicker and cheaper to produce, working out more cost-effective per unit than THT. That being said, it’s harder to inspect the boards once they are complete which means that more money must be spent investing in technology that can handle this task.

The fact that SMT is cheaper and more efficient has led many to believe that Through-Hole assembly techniques will one day become obsolete. However, there are certain products that will always require a stronger bond between the components and for those, the THT method will be longer-lasting and more durable.

Which should you choose?

There is no one-size-fits-all approach, though SMT tends to be the favoured method nowadays. That being said, which technique you choose to use will very much depend on the purpose of your products, your budget, durability and your chosen production methods.