Choosing the new SMT Assembly can be arduous. Engineers must analyze the merits of hundreds of varieties and parts, whether in stock, how future supply looks, 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）
Special Offer: $1 for 5 PCB Assemblies!
Please email [email protected] for details.
1. Brief Introduction Of Through-Hole Technology
Through holes are considered 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 and inner layer tracks of the printed circuit board.
It gave way to plated through-hole technology, 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 ）
2. A Brief Introduction To Surface Mount Technology
Surface mount technology became known in the 1960s, and its 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 connect 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 is to the PAD with the help of stencil solder.
A pick-and-place machine is also responsible for initially placing the components on the solder paste set above the PAD.
After setting, these components must 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）
3. Differences Between Spaces
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 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）
4. Higher Pin Count In SMT Assembly Than Through-Hole Technology
SMT beats THM because it can hold a 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.
On the other hand, surface mount components 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)
Special Offer: $1 for 5 PCB Assemblies!
Please email [email protected] for details.
5. SMT Assembly Components Are Usually Cheaper Than Through-Hole Components
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 limits the routing area in any board with 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 the cost for placing components than a surface mount.
On the other hand, the surface mount assembly has a plurality of terminals soldered to the tubular body.
Compared with flat chip vias used, the cost of these components is much cheaper.
(Small components on the PCB)
6. Surface Mount Technology Is More Helpful For Assembly Automation
SMT can be produced in high volume at much lower costs because 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）
7. Through-Hole Technology Pays More Attention To Performance
How 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 through-hole components 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 SMT PCBA.
So, performance-wise, THM has a lot of advantages over SMT.
（Electronic chip components on green printed circuit board）
8. The Technical Cost Difference Between Through Hole And Surface Mount
Undeniably, the THM issue 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 a much higher volume and soldering can be automated, they are cheaper.
9. How To Choose PCBA Technology
| SMT assembly | Through-hole | |
| 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
Through-hole:
Advantage:
- The leads must be inserted through the drilling holes. It makes the component sturdier. They can handle much environmental stress, mechanics, heat, and pressure.
- PCBs of THM are also suited for collisions or extreme accelerations, so it is ideal for advanced applications like military or aerial equipment or transformers.
- THM can be easily replaced, so the prototype is mainly for testing applications.
Disadvantages:
- The bigger component size and one-sided availability make the manufacturing cost higher.
- The components of THM are also placed and soldered manually, leaving little room for automation like SMT, so it is expensive.
Boards with THM components must also be drilled, so no tiny PCBs come at a low cost if you use THM technology.
（Through-hole）
SMT Assembly-Surface mount technology:
Advantage:
- 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 predominantly use the SMT because they weigh less than the THM boards.
- The components are packed tight on the board, so this is a distinct advantage, with many electronics focusing on reducing the size.
- The SMT components are smaller and can be placed much faster during assembly, so the production cost is low.
（Surface mount technology）
Disadvantages:
- 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 can effectively lead companies to push low-volume boards to higher prices, Just because of the significant capital investment.
- The surface mount technology requires a lot of precision due to the components' buried vias and size.
- The design also involves a lot of skill because any violation of the pad layout guidelines could result in tombstoning. That means the product can be reduced largely.
Summary:
There are certain advantages and disadvantages to both SMT and THM.
SMT's primary applicability and demand come from many electronic devices 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, and environmental durability make it ideal for aerodynamics and military applications.
Suppose you need PCB assembly, whether 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.
Special Offer: $1 for 5 PCB Assemblies!
Please email [email protected] for details.