One of the first decisions in making a PCB is to choose the style and type of components we are going to use. This mostly depends on the electrical requirements of the PCB. However, once we meet the electrical requirements, there are a variety of available footprints and configurations to choose from. The type of components we choose will affect the appearance and size of the finished PCB. In the early days, we dealt with components having long leads by inserting them manually into plated through holes on the PCB. We then soldered the leads to form strong interconnections with the holes. This is what we know as a through hole PCB assembly.

With the passage of time, manufacturers prefer to use a modern assembly method that relies on components whose leads are only attached to the surface of the PCB. This method doesn’t require any mating hole. This is what we know as the Surface Mount Technology (SMT). However, it was known as planar mounting in the earlier days.

Today we will look at both of these techniques and we will help you in choosing between them according to your needs.

Through hole PCB

Through hole components are mostly available in two types of packages which can be axial or radial. Axial through hole components have electronic leads along their axis of symmetry. A basic resistor is a classic example of a through-hole component as you can notice that the electrical leads are present along its cylindrical axis of symmetry. Other examples are inductors, capacitors, and diodes.

On the other hand, radial components have electrical leads which are projected from the same surface of the component. These are often preferred as it allows us to mount them on a board in a way which takes up a smaller space.

Manufacturers discovered through-hole components when they were looking to improve efficiency and they weren’t concerned with the aesthetics. It was a tradeoff between mechanical stability and signal integrity. Manufacturers were not focusing on the required space of the components. Therefore, they didn’t concern themselves with signal integrity problems.  However, as demand for PCBs increased, manufacturers had to rethink their approach. Now power consumption, board space requirement, and signal integrity became a concern. Manufacturers now want to use components that come in smaller packages and provide the same functionality. This is where we look towards surface-mount components.

Pros and Cons of Through hole PCB

Pros 

Through-hole technology is very reliable as there is a stronger connection between the PCB and the components. This is why most of the manufactures still use through-hole technology. We especially rely on this technology in those applications where the PCB goes through fast acceleration and suffers from increased stress.

It is very easier to replace through-hole components. That is why it is easier to perform tests by using through-hole technology. This is the primary reason for using through-hole for prototyping.

Cons

These components need a lot of space to place them on a PCB as compared to the surface-mounted components.

We have to manually perform most of the through-hole operations.

Surface Mount PCB

Surface-mounted components dominate the modern PCB design. These components don’t rely on electrical leads. We can solder these components directly on the PCB surface during the assembly process. Surface-mounted components are mostly used where we have limited space and we are concerned with the component size. The major benefit of surface mounted components is that we can use them at high frequencies and speeds without facing any signal integrity problems.

Pros and cons of Surface Mount PCB

Pros

Surface-mounted components are much smaller in comparison to the through-hole components. This allows us to increase the overall density of the finished electronic product.

We can place surface mounted components on both sides of the PCB.

We can reduce the production time by using a Pick and Place machine for automating the process.

Cons

These components are not suitable for applications involving high power consumption.

We cannot use surface-mounted components for testing or prototyping of circuits.

Overall Comparison between Surface Mount PCB and Through-Hole PCB

With this detailed comparison, we can safely conclude that surface mounted assembly is more cost-effective and efficient than the through-hole assembly. Most of the advanced electronic products involve surface mount technology. However, when we require special electrical, thermal, and mechanical applications then through-hole technology is still a viable option.

It is a fact that technology and science are making continuous progress. And it is also a fact that new products will replace old products. But it doesn’t imply that it is necessary to eliminate conventional technology. For instance, multi-layered PCBs are more efficient than single-layered PCBs. However, they are also more advanced and complex. Can we use them in the control dials of an aircraft? Yes. Should we use them in a simple toy car or a clock? Definitely No. Merits of some conventional things can still make them play a vital role in the future to come.