The PCB technology to design PCB came to fulfill the need for a strong and effective circuit design. Throughout the evolution of the PCB until the 1980s, the electronic components that used to come contained metallic leads. These leads were used to fix and firm the components on the circuit by soldering them on the other side. For this purpose, blank space was left on the PCB circuit and holes were drilled. As a consequence, the technology came to be known as through hole technology. Though surface mount technology took over after 1980s, the through hole technology has not lost its existence. This is because of some exclusive benefits of the through hole technology that surface mount technology cannot offer.

Features of through hole technology
The technology approach is simple. The electrical circuit is designed on a software and printed on a PCB. The PCB is then fabricated with conductive links etched on the PCB substrate that connects the electronic components to realize a circuit. Appropriate amount of spaces is left on the PCB to accommodate the components. Holes are drilled on the PCB so that the leads of the PCB are put in place and soldered. Soldering is done on other side of the board. As a result, the other side of the board is rendered fully or partially useless.

The through hole technology is particularly suited for leaded components. The leaded components then again used to come in two variants. One with axial leads and the other with radial leads. The axial leads are horizontal components with the leads at straight angle. These components lack the height factor but has considerable length. When used in a circuit, they result in a low height long length circuit. So, these components were particularly used when low heights were required.

Another variant of the components comes in radial form. Here, both the leads come out of the same side and are parallel to each other. These components are generally vertical in nature. When used in a circuit, they increased the height of the circuit but reduced the height of the circuit. Therefore, if a circuit has to be small lengthwise as in case of a CFL, these are the components to be used. Alternately, the axial components are used as radial components by bending one of the legs in parallel to other leg. This way the horizontal configuration of the axial components can be changed to radial.

Advantages

  • This PCB is known for its strong soldering and firm contacts. They can bear good amount of shocks and jolts and other mechanical stresses.
  • The heat dissipation is good due to good amount of exposed conductive surfaces and large size of components.
  • The circuits can be given desirable dimensions bu employing the use of axial or radial components.
  • The testing of the circuits is easy as they are compatible with breadboard sockets.

Disadvantages

  • When compared to the surface mount technology, the size of the circuits is greater.
  • The data transfer speed is low in this kind of PCB.
  • The other side of the PCB is of little use due to lead soldering.
  • The cost of manufacturing is high due to drilling of holes in the board.