What is Through Hole Technology(THT)?

THT (Through-Hole Technology) is a crucial technique in PCB assembly. Although surface-mount technology (SMT) has become increasingly popular in modern electronics manufacturing, THT still plays a vital role in certain applications. This article delves into the details of THT technology, including how it works, its areas of applicability, and a comparison with other PCB assembly methods.

THT technology is a traditional PCB assembly method that involves passing the leads of electronic components through holes pre-drilled in the PCB and soldering them on the opposite side of the board. This is different from SMT, where component leads are directly attached to the surface of the PCB without the need for holes.

The working principle of THT is straightforward yet effective. First, holes are pre-drilled on the PCB to match the diameter of the component leads. Next, the component leads are inserted into these holes. Finally, soldering is performed on the bottom side or the opposite side of the PCB to create connections between the component leads and the solder pads on the PCB. Various methods, including manual soldering and wave soldering, can be used for this soldering process.

THT technology is particularly useful in the following scenarios:

Large Components: THT is typically more suitable for components with large leads, such as resistors, electrolytic capacitors, and inductors. These components have robust leads that are easy to insert and solder.

Mechanical Strength: Due to leads passing through the PCB and being soldered on the bottom, THT soldering usually results in higher mechanical strength, making it important for applications subjected to physical impacts or vibrations.

Heat Tolerance: THT solder joints can generally withstand high temperatures, which is crucial for electronic devices operating in high-temperature environments.

Manual Assembly: In cases of low-volume production or situations requiring manual assembly, THT technology is highly useful. Soldering THT components is typically more straightforward, eliminating the need for expensive automation equipment.

However, it's essential to note that THT technology also has its limitations. It's not suitable for high-density PCBs because of the larger pitch between leads, which doesn't meet the requirements of compact layouts. Additionally, THT soldering often occupies more PCB space.