What is THT (Through-hole technology)?

　　THT technology is the abbreviation for Through-hole technology and ＂thru-hole＂ . It is a technique used to assemble electronic components onto printed circuit boards (PCBs). The distinguishing feature of this technology is that the electronic components have metal pins, referred to as “THT components.” These pins pass through the plated-through holes (PTH) on the PCB and are joined to the PCB through soldering with tin. This completes the assembly of electronic components onto the PCB.

　　THT components are known for their simple structure, straightforward assembly process, and ability to withstand harsh conditions such as high temperature and humidity. The assembly of THT components can be done manually through soldering or using high-volume production techniques like 波峰焊(Wave Soldering) . Some THT components can even be assembled using automated Surface Mount Technology (SMT) techniques.

　　Although SMT technology has become increasingly popular in modern electronics manufacturing, allowing products to become smaller, lighter, and thinner, THT technology still finds application in student electronics experiments, small-scale maker projects, and products that require resistance to high temperature and humidity.

The characteristics of THT (Through-hole technology) packaging technology

　　Common THT (Through-hole technology) components can be broadly categorized into the following three types:

• THT-packaged electronic components
• THT-packaged integrated circuits (ICs)
• THT-packaged modules

　　The introductions are presented separately as follows:

THT-packaged electronic components

　　This is the most common type of THT (Through-hole technology) component, and it encompasses the commonly seen electronic components such as resistors, capacitors, and inductors. Each of these components has various types of THT packaging, which give them different characteristics. The diagram below illustrates some commonly encountered THT electronic components.

Here are images of some dual-ended and three-pin electronic components – resistors, capacitors, and bipolar transistors.

THT-packaged integrated circuits (ICs)

　　THT-packaged IC (Integrated Circuit) is also a common category in Through-hole technology. Depending on the required pins and dimensions of the IC, different packaging names are used. The table below lists some commonly used abbreviations for THT-packaged ICs for readers’ reference. The image below shows a photo of an SOP24 component.

Here are some photos of IC (Integrated Circuit) components in SOP8, SOP16, and SOP40 packages.

THT-packaged modules

　　There are many types of circuit modules packaged with THT (Through-hole technology). Taking the LED seven-segment display as an example, the THT-packaged LED seven-segment display is assembled with the front side serving as the light-emitting surface and the back side connecting to the pins and PCB. The image below shows a model OPD-AD4010, which is a 0.4-inch high LED 14-segment display with two characters. In the image, you can see the light-emitting surface and the pin structure underneath.

The scale of THT (Through-hole technology)

Comparison between THT 0.39″ character height single-digit 7-segment display and Type-C connector

　　On the left side of the image is the OPD-S3910 single-digit 7-segment display from Leap Electronics with a character height of 0.39 inches. On the right side is a USB Type-C connector. By comparing the graphics, we can get a rough idea of the size of the 0.39-inch THT 7-segment display.

The assembly methods for common Through-hole technology (THT) components

　　THT (Through-hole technology) assembly methods can be broadly divided into two types:

• Directly connecting THT components using pins
• Assembling THT components onto a PCB

Let’s discuss each method separately.

Direct pin connection THT(Through-hole technology) components

　　Since almost all circuit components are available in THT (Through-hole technology) packaging, direct soldering of THT component pins is a convenient approach when dealing with relatively simple circuits. This method is commonly used in student circuit experiments or when prototyping in small quantities. Below is a tutorial video demonstrating the assembly of a 24V battery indicator light using a THT-packaged LED bulb and resistor. It provides a reference for the soldering process.

Assembly on a PCB board

　　The most common method of assembling THT (Through-hole technology) components on a PCB board is called wave soldering process. This article does not delve into the details of wave soldering. Below is a two-minute video found on the internet that demonstrates the wave soldering process. You can see that when the PCB passes through, a raised wave of solder touches the bottom edge of the PCB, completing the assembly. The second method of assembling THT components on a PCB board is by manually inserting the components into the PCB and using manual soldering techniques. This method is often used for low-volume production or when the number of components is small. For mass production, wave soldering is commonly employed.

THT (Through-hole technology) is also commonly known by several other names

　　THT (Through-hole technology), also known as through-mount technology, has various alternative names. Taking Taiwan as an example, for THT-packaged IC integrated circuit components such as SOP24, which have symmetrical dual-sided pins, these pins are also referred to as DIP packaging (Dual in-line package). THT components are commonly known as “DIP components”.

　　Furthermore, since THT components typically have extended pins (LEAD) outside of the component structure, these pins are often referred to as PIN pins. Sometimes, THT components are also referred to as “components with PIN pins”.

　　Additionally, as THT components are mostly assembled using wave soldering technology, they are sometimes referred to as “Wave Soldering components”.

Conclusion

　　This article provides a concise explanation of the names and aliases of THT (Through-hole technology) components. It also shares three major types of THT components and a comparison table of their sizes. Finally, it briefly introduces two assembly methods for THT components. It is hoped that readers will gain a preliminary understanding of THT components after reading this article.

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