Choosing the new SMT Assembly can be arduous. Engineers must analyze the merits of hundreds of varieties and parts, whether it is in stock, how future supply looks like and the replacement cost of parts. Whereas all these are vital aspects to choosing a type of PCB, there is a much more fundamental question that we should be asking – whether to select surface mount technology or through a hole?
In this article, we will find out the applicability of both technologies.
（SMT technology in factory production line）
Through holes are considered to be one of the older designs by many, whereas surface mount is pretty new. And to some extent, it is undeniably true, but if we think about practical applications, the through-hole technology is still significantly better in specific scenarios. In the 1950s, printed circuit boards came with tracks written on only one side.
When you insert the leads of a component into the board, you increase the drilled holes. Therefore, the negative electrode side has an element soldered to the copper on the board. The later stages saw the introduction of tracks on both sides of the boards, as well as inner layer tracks of the printed circuit board. It gave way to the technology of plated through-hole, making it possible to attach components to the inner layer of the circuit board, improving the concept of through-hole PCBA assembly.
（Caption: Radio Components on PCB using Through-Hole Technology ）
Surface mount technology became known in the 1960s, and the applicability slowly rose in the 1980s. This technology was known as planar mounting in the beginning. The technique of surface mounting involved SMDs or surface mound packages. Components in this board have lead surrounding or underneath.
What separates surface mount from through-hole technology is that there is no need to drill holes in the circuit board to have a connection between the tracks and the components. Establishing relationships through leads. The ingredients are in direct touch with the PADs of the circuit board And add solder paste to PAD with the help of stencil solder. There is also a pick and place machine, which is responsible for placing the components on the solder paste set initially above the PAD. After setting these components, they have to be placed in a reflow oven or introduced in a vapor phase to be soldered permanently in the surface mount PCB assembly.
（Caption: Microchip with Surface Mount PCB Technology）
In the case of surface-mounted technology, the PCB can mount more components due to two factors. First, the elements of the SMT are smaller themselves, and then they can also be placed on either side of the board. The space problem that is prominent in the through-hole is overcome in the surface mount technology so space can get smaller, lighter, faster, and more powerful.
（Printed circuit board with SMD and IC on board）
SMT beats THM in this regard because they can hold much higher pin count. Pin count on a component board is simply the lead count of the component, which is the total number of the part leads that a printed circuit board can fit.
The leads of through-hole components have become replaceable with the invention of smaller parts called vias. They allow conduction between the various levels of the PCB, and by doing so, eliminate the need for through-hole leads. Surface mount components, on the other hand, are much higher in performance, have shorter points, and the pins are much more interconnected, which leads to better speed.
(Beautiful pin lines on printed circuit boards)
The through-hole method requires drilling holes in the empty side of the board. It is a task that takes a lot of time and costs a hefty amount. THM also makes the routing area limited in any board that has multiple layers. It is only because the holes should pass through all these layers. When we look at the through-hole PCBA, the assembly side comes at a fraction of a cost for placing components than a surface mount.
On the other hand, the surface mount assembly has a plurality of terminals which soldered to the tubular body. Compared with flat chip vias used, the cost of these components is much cheaper.
(Small components on the PCB)
SMT can be produced in high volume at much lower costs because the SMT has the possibility of assembly automation. It also results in lower costs during production.
Automated assembly can save PCB assembly time even more. Many PCB suppliers currently have production machines with surface mount technology. It can be assembled accurately and quickly.
From this point of view, it is faster and more advanced than through-hole technology. If you are looking for assembly speed and need to produce PCBs in large quantities, you can choose surface mount technology. Ask your PCB supplier if they can provide it.
(SMT production line machines）
The way through-hole components are soldered makes it durable in high heat and shock scenarios. The through-hole elements have long led, and these can be inserted through the drill holes, ultimately being fastened to the copper pads underneath. It is a secure process that is much more reliable than the mounting style in SMT. It also makes it possible for through holes to endure higher stress conditions.
The components of the through-hole are also more significant, and while that makes space an issue, it helps with high power applications. Parts can also be easily removed and replaced in urgent situations, which is not right in the case of SMT PCBA.
So, performance-wise THM has a lot of advantages over SMT.
（Electronic chip components on green printed circuit board）
Undeniably the issue with the THM is the drilling cost, which makes it more expensive and time-consuming than the SMT. The components also have to be hand soldered on the board.
Since the SMT PCBA offers much higher volume and soldering can be automated, they are cheaper.
|Unsuitable for high stress||Surroundings||Good for high stress and high heat|
|Less expensive production||cost of production||More expensive due to manual soldering and drilling|
|Prototyping or production||The level of development||Proof of concept or prototyping|
|Placed on both sides||Circuit board layout||Placed on one side|
|Low Power||Main application||High power|
10. Advantages And Disadvantages Of Through Holes And SMT Assembly
- The leads must be inserted through the drilling holes. It makes the component sturdier. They can handle a lot of stress from the environment, mechanics, heat, and pressure.
- PCBs of THM is also suited for collisions or extreme accelerations, so it is ideal for use in advanced applications like military or aerial equipment, or transformers.
- THM can be easily replaced, so the prototype is mainly for testing applications.
- The bigger component size and one-sided availability make the manufacturing cost higher.
- The components of THM also placed and soldered manually, leaving little room for automation like SMT, so it is expensive.
Boards that have THM components also must be drilled, so there are no tiny PCBs that come at low cost if you are using THM technology.
- SMT has the fewest components and we can place them quickly. Components can be mounted on both sides for automated welding. All these make it much cheaper.
- Small, lightweight PCBs are all predominantly using the SMT because they are much smaller than the THM boards and weigh less. The components are packed tight on the board, so with many electronics focusing on reducing the size, this is a distinct advantage.
- The SMT components are smaller and can be placed much faster when the assembly is happening, so the overall cost of production is low.
（Surface mount technology）
- SMT is not without challenges despite the many advantages it offers. We can quickly place components, and the entire thing can be automated – but the caveat is the machines that can do that cost very high. It effectively can lead companies to push low volume boards to higher prices, Just because of how significant capital investment is.
- A lot of precision is required in the surface mount technology due to the buried vias, and size of the components.
- The design also involves a lot of skill because any violation in the guidelines of pad layout could result in tombstoning. That means the product can be reduced largely.
There are certain advantages and disadvantages to both SMT and THM. The primary applicability and demand for SMT come from the fact that many electronic devices are pushing for a smaller size, which SMT can provide. It is why 90% of all the printed circuit boards made today are SMT.
However, there is no denying the resilience of the THM in specific applications. The high stress, thermal, environmental durability makes it ideal for aerodynamics and military applications.
If you need PCB assembly, whether it is through-hole technology or surface mount, OurPCB can provide you with professional technology. What are you waiting for, you can contact us now for professional services.