A comprehensive introduction to THT through-hole technology

Through-hole or THT technology is drilling holes into a PCB and electronics components are supposed to solder in that hole to connect tracks on PCB. It is an older technique than surface  mounting. Despite the fact that it is an older technology, thru-hole PCB assembly has advantages.  Through hole mounting strengthens the bonding between a circuit board and its components,  resulting in more robust, shock-resistant, and impact-resistant devices. 

Why Through Hole PCBA technology: 

PCB design evolved from single-sided boards to double-sided boards, and finally to multi-layer  boards. To match the needs of contemporary electronics, through hole assembly is tough. In  today’s PCB production, SMT technology has virtually overtaken through hole fabrication.  However, through hole assembly is still required in some applications, such as electrolytic  capacitors, connectors, and big transformers. 

PCB DIP connectors have better mechanical strength than most SMD connections. In contrast, the bonding strength of PCB surface mount components does not surpass  that of the multilayer PCB board surface. Process fixing components for through hole PCBA  technology is best suited for high-reliability devices that require strong connections between  different conductive layers of PCB in PCBA. The Surface Mount Device (SMD) is merely soldered  to the circuit board’s surface through SMT assembly techniques, while the lead of the through hole fastening DIP component goes through the whole circuit board, allowing the part to endure greater environmental stress. If too much solder is used, it may go into other connections and produce a short circuit. If too little solder is used,  then the joint may not be strong enough. Cold solder junctions can shatter, and getting the  connection too hot might harm the components or the board. 

As a result, the through hole PCBA assembly technique is typically employed for military,  automotive, and aerospace goods with high acceleration, collisions, or temperatures. Through hole assembly technique is also appropriate for testing and prototyping applications that need manual  device adjustment and replacement. 

Characteristics of THT Technology

When using through hole assembly, one begins with a PCB and the PCB components. Then  holes are drilled into the board that is just the right size to accommodate component leads. After  the leads are inserted into the holes, they are soldered to the board, which secures them in place  and forms a strong, long-lasting link. This is the distinguishing feature of through-hole assembly  that makes it so dependable and allows it to continue servicing numerous sectors. 

Through hole technology allows multiple components to be mounted on the PCBA,, and engineers employ two types of components throughout this procedure. These are some examples:

Axial leaded components

The most striking feature of an axially leaded component is its symmetrical form. This sort of DIP PCB component frequently has a cylinder-like form, with one or more leads extending  from both ends. When each wire end is inserted through a hole, the axial component is low  on the circuit board and might occupy a larger or smaller area depending on how the leads  are positioned. These components may include resistors, inductors, and capacitors. 

Radial leaded component

Radial leaded components are often cylindrical or rectangular box-shaped figures that  incorporate various capacitors, resistors, and inductors. The fundamental distinction  between these components and axial leaded components is that the former have leads that  originate from one side rather than both ends. Attaching these parts to your PCB board  takes significantly less space than utilizing axial leads, but also provides less placement  freedom. 

Advantages of Through Hole Technology

Strength of Bonds

Through hole assembly includes inserting necessary components through a circuit board and  then connecting them with a metal solder, which strengthens the connection between the circuit  and its components. When using electrical equipment, it is critical that all of the circuit’s  components stay intact. Because of this, through hole assembly is a better choice for high-risk  electrical equipment than alternative methods such as surface mount soldering. 


Stronger linkages between circuit components imply greater durability and the ability to  withstand tougher circumstances without significant wear and tear or damage. If there is need of  an assembly that is suitable for aerospace industries or the usage of heavy machinery, through hole assembly technology is the best option and will last longer than others. A long-lasting electrical circuit will  save money on replacement costs in the long run. 


The last thing is to utilize time wondering about whether PCBA will hold up every time  employed to machine. Because of the reliability of drilling and soldering technologies, using  through hole PCBA assembly solutions eliminates this uncertainty. A reliable product may relieve  your worries and help you maintain a high level of efficiency in your operations, which is essential  in a tough or fast-paced environment.

PCBA Through-Hole Soldering Machine

Nowadays, there are a number of through-hole soldering machines available and all of them have  different salient features. Sometimes, these machines are also known as Soldering Robots. The  main usage of these robots is soldering the electronic through hole components to PCB. Mostly  Soldering machines work on following two principles:

Wave Soldering: Wave soldering, as the name indicates, is used to join PCBs and parts  using a liquid “wave” created by motor motion. Tin has been melted in the liquid. It is done  in a wave soldering machine. 

Selective Soldering: Selective Soldering is the use of a solder fountain to solder specific through hole DIP components on a PCB. A flux spray, preheater, and a soldering pot that feeds  a solder fountain are all part of the machine. The solder fountain or head moves to the  soldering position from beneath. 

Let’s have a quick overview of both techniques in the following caparison table:

Selective Soldering 

Wave Soldering

  • Required less post-soldering rework
  • Consumption of Solder is less 
  • Relatively not the best option for mass  soldering 
  • Overall operating cost is relatively less
  • Process flexibility is less in this case 
  • Requires more post-soldering rework
  • More solder is required in this  technique 
  • Best for mass soldering 
  • Overall operating cost is relatively  more 
  • Process flexibility is more in this  technique

Following are some noticeable features of Selective soldering robots as follows 

  • Some robots have a very advanced design, and solid structure and are beautiful physically  while remaining practical and more reasonable. 
  • Among all available robots, 5D and 6D are mostly used with X, Y1, Y2, Z, R, and feeding  systems for soldering wire. All five or six-axis motions are controlled actions and can be  performed by stepper motors to make 6D motion more precise and smooth.
  • In robots, there is a mechanism of self-cleaning soldering tip, which enhance the quality of  soldering. 
  • Mostly all robots have a 400W of heating recovery system, which helps in quick  temperature of the robot’s tip. 
  • Such robots provides user vast variety of soldering tips to fulfill different requirements. 
  • When feeding solder wire, a break tin solder wire feeding system may punch holes and  decrease burst tin, which causes the flux to remain on the PCB when soldering at high  temperatures, hence improving soldering quality. 
  • These robots have a tip cleaning system, using a high-efficiency electric steel brush to clean  the soldering tip. It effectively removes leftover tin from the soldering point.

This is the end of the introduction of through-hole technology. If you have different opinions or find wrong content on the website, you can contact us by email. FS Technology not only provides high-quality PCBA services, but also is committed to spreading more technology-related content.