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THT PCB – the assembly technology being replaced by SMT in PCBA


From 1903 to the present, if the application of PCB assembly technology and development point of view, PCB circuit board technology development can be divided into three stages – THT, SMT and CSP. As the first stage of PCB development technology, THT PCB has important significance for the advancement of the PCB industry.

THT is used for the construction of various printed circuit boards. It is the process of staging the PCB components. This mounting is done with leads using a through-hole. Through-hole components have tight physical bonds to the PCB board, which makes it very strong and durable. THT PCB in the automotive electronics, military and aerospace industries cannot be replaced in a short period of time, but it has been gradually replaced by SMT in the consumer electronics industry.

What does THT mean?

What-does-THT-meanTHT means through hole technology. THT dominated the electronics industry until SMT was introduced. For those components that need to go through any mechanical stress, THT PCB is the best choice.

How do through-hole work?

Through-hole technology refers to the staging or mounting scheme of components on the PCB board. Through-hole is used for electronic components. Leads are connected to the components and these leads are then inserted into the holes. These holes are drilled in the PCB. After the insertion of the leads, these are soldered. The soldering to pads is done on the opposite side.

The insertion and then soldering are done either manually or with the help of mount machines. Through-holes are used for the installation of different components on the PCB board. Components like capacitors or inductors or resistors are inserted onto the PCB board. A through-hole is such a hole that passes through anything that is either drilled or milled with the help of a hand or any other machinery.

What is THT in PCB?

THT is one of the most popular technologies and processes in the traditional electronics assembly industry, but now it is being replaced by SMT as the electronics industry develops.THT uses components with leads, and designs the circuit connection leads and mounting holes on the printed board.

Then it establishes long-term mechanical and electrical connections by inserting the component leads into the through holes reserved on the PCB, temporarily fixing them and then soldering them on the other side of the substrate to form a reliable solder joint. Simply, through-hole technology is the insertion of leads. Through hole means that the components are inserted into the printed circuit board and then soldered in place with solder.

What’s the processes of THT PCB assembly?

Firstly, the equipment required for the THT PCB assembly is soldering iron, solder paste printing machine, wave soldering machine, reflow soldering machine, etc.

The general process flow is: component insertion → PCB loading → wave soldering → PCB unloading → DIP lead frame trimming → cleaning

What is the advantage and disadvantage of THT PCB?

advantage-and-disadvantage-of-THT-PCBHere are some of the advantages and disadvantages of THT PCB.

THT PCB has several advantages. One of the biggest advantages is that the bond between the components and the PCB board is quite strong. That makes it durable. This is perfect for those components that will undergo any mechanical stress or environmental stress. THT printed circuit boards are suitable for those components that undergo heat changes like transformers, etc.

Testing and swapping are also very easy in through-hole printed circuit boards. TCT printed circuit boards are well-built. Through-hole printed circuit boards are more temperature resistant and stress resistant. There are stronger, reliable, and well-built.

Here are some of the disadvantages of THT PCB. THT printed circuit boards take time and are time-consuming as well. Since the leads of the components are inserted into the PCB board, the board requires to be drilled before the insertion of components.

The components are restricted to one side. Also, the routing area is limited. Due to the soldering process involved, the solder points become less strong and durable. THT printed circuit boards are more expensive as well.

Where are through-hole PCBs used?

Through-hole printed circuit boards are used where mechanical stress is involved and heat change might occur. These printed circuit boards are used where there is an involvement of such components that undergo stress. These printed circuit boards are mainly used for military purposes and in aerospace too.

What’s SMT and how does it work?

Whats-SMT-and-how-does-it-workSMT is also termed surface-mount technology. It works by mounting the components directly on the board. It involves no drilling, and no insertion rather the components are directly placed onto the surface of the board. This technology is used more now because electronic designs have become more complex.

In SMT PCB technology, the components are soldered with the help of production lines. The components are placed directly on both sides of the board. Surface-mounted technology is more efficient, it is less complex. The engineers widely rely on surface-mounted technology because the designs have become more complex.

THT PCB? SMT PCB? How to choose?

SMT printed circuit board means surface mounted while THT PCB involves through-holes. Components are not drilled in SMT printed circuit board. When it comes to choosing between THT and AMT then it depends upon the application, if PCB is required for communication purposes or medical devices SMTs are used but for military purposes mainly THT printed circuit boards are used.

Further, based on speed, frequency, and efficiency, we choose the printed circuit board. Reliability and durability are also considered while choosing the PCB.

What is the difference between THT and SMT ?

The difference between SMT and THT is such that in through-hole technology drilling is required while in SMT technology no drilling is involved. In surface-mounted, the components are directly placed on the board while in THT technology it requires to be inserted.

The difference is in cost too. The efficiency of both the printed circuit boards is different and so are the frequencies. The time to mount the components is different in both printed circuit boards. The temperature resistance in THT PCB is more as compared to SMT PCB.

SMT simplifies the process of production, which is complex in the case of through-hole technology. The material cost of surface-mounted technology is also less compared to THT PCB. The frequency characteristics of surface-mounted are better as compared to THT PCB. The transmission speed of signals is high too.

The geometric size of the surface-mounted PCBs is also smaller, and they are less expensive too, although THT PCB is stronger and more durable. The components can be placed quickly in the case of surface-mounted technology, so surface-mounted printed circuit boards are used more and they have more advantages as compared to THT PCB.

In terms of reliability and durability, through-hole technology is better. The temperature resistance and stress resistance is also high in through-hole technology. But today the engineers have to make very complex designs and compact too so this is possible in SMT PCB.


As electronic products and components continue to evolve, the technology required for PCB assembly (PCBA) continues to evolve with the times,which places great demands and challenges on PCBA makers. Both SMT and THT represent the development of the PCB industry. They both have their own strengths and weaknesses and specialize in their application industries, and both bring convenience to the electronics manufacturing industry.

Although THT is slowly being replaced by SMT in many industries, but its former position is unshakable. I believe that in the future, the PCBA industry will have faster development and more advanced technology, let’s wait and see together.



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