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Quick answer
THT stands for Through-Hole Technology: the metal pins of the component pass through holes in the PCB and are soldered on the far side — the older assembly method, and still the right one for many displays. It’s known for its simple assembly, durability in harsh conditions, and remains useful for certain applications despite the rise of SMT.
Table of Contents
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 Wave soldering. Some THT parts can be placed by automatic insertion machines, but OPTO PLUS THT displays must still be wave- or hand-soldered; they cannot go through reflow.
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 photo below the table shows several DIP-packaged ICs.
| Package Name | # of pin | W*L*H (mils) | pitch (mils) |
| MDIP8 | 8 | 365*250*130 | 100 |
| MDIP14 | 14 | 755*250*135 | 100 |
| MDIP16 | 16 | 760*250*130 | 100 |
| MDIP18 | 18 | 900*250*155 | 100 |
| MDIP20 | 20 | 1026.5*260*130 | 100 |
| MDIP24 | 24 | 1260*280*130 | 100 |
| MDIP28 | 28 | 1450*540*150 | 100 |
| MDIP40 | 40 | 2056.5*550*145 | 100 |
Several DIP (dual in-line package) ICs, from 8 to 40 pins — all through-hole parts.
THT-packaged modules
There are many types of circuit modules packaged with THT (Through-hole technology).
THT-packaged module example – LED 14-segment alphanumeric display OPD-AD4010
Taking an LED alphanumeric display as an example, a THT-packaged LED 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.
THT-packaged modules Example -LCD Module with PIN for arduino photo
The scale of THT (Through-hole technology)
THT 0.39″ single-digit 7-segment display vs a Type-C connector
On the left side of the image is the OPD-S3910 single-digit 7-segment display from OPTO PLUS LED corp 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 DIP24, 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”.
THT displays cannot go through reflow soldering
Before comparing any optical specification, please confirm one process question first: does your production line use reflow or wave soldering? Through-hole LED displays are not compatible with the reflow process. If your line only has reflow, choose the SMD version of the display. This one answer decides the THT or SMD question before any other specification. THT displays are assembled by wave soldering for mass production, or by hand soldering for small quantities.
Wave soldering conditions
The recommended wave soldering conditions for THT LED displays are:
- Pre-heat: 100 °C or less, for 60 seconds or less, measured at the LED pins
- Solder bath: 260 °C maximum
- Peak wave temperature: 245–255 °C for 3 seconds (5 seconds maximum)
- One soldering pass only. Do not pass the board through the wave twice.
- Board layout: keep the display at least 5 mm from the PCB edge. For 90-degree bent-pin types, keep at least 10 mm.
Hand soldering and rework
Use a temperature-controlled soldering iron of 30 W or less. The reference conditions are 300 °C for leaded solder and 350 °C for lead-free solder. For blue, green, and white products, the limit is 280 °C for 3 seconds or less. Some datasheets specify stricter conditions, for example 15 W and 260 °C within 4 seconds. The datasheet of the selected part number always has priority.
For rework, finish within 3 seconds at 350 °C, and do not let the iron tip touch the copper foil.
Lead bending and storage
- Bend the leads before soldering, at room temperature. Keep at least 3 mm between the bottom of the lens and the bending or soldering point. Do not bend the same lead more than twice.
- Storage before opening: 30 °C or less and 60 %RH or less.
- After opening, THT displays have no floor life limit. SMD displays are different: they should be used within 4 weeks (MSL 2a), or baked before use.
- ESD: keep the workstation static potential at 150 V or less, and the line humidity at 40–60 %. InGaN products (blue, green, white) are the most sensitive.
THT or SMD? A short comparison
| Condition | THT | SMD |
|---|---|---|
| Production line | Wave soldering or hand soldering | Reflow soldering |
| Environment | High temperature, high humidity, vibration | Normal indoor use |
| Mechanical needs | Strong pin retention, panel mounting | Thin design (down to 3.1 mm), high density |
| Smallest standard digit height | 0.3 inch (OPx-30xx) | 0.2 inch (OPx-20xx) |
| Floor life after opening | No limit | 4 weeks (MSL 2a) or bake |
THT LED Products from OPTO PLUS LED
- THT LED Lamps — through-hole LED lamps for wave-soldering lines.
- 7-Segment LED Displays — THT display versions covered by the soldering conditions in this article.
Conclusion
THT (through-hole) components are also called DIP components, components with PIN pins, or wave soldering components. They come as discrete electronic components, ICs and modules such as LED displays, and they are assembled either by soldering their leads directly or by mounting them on a PCB, where wave soldering is the usual mass-production method. Their strengths are a sturdy joint and tolerance of heat and humidity; the cost is board space and a slower assembly than SMD.
Our advice: if every other part on your board is SMD, check whether an SMD version of the display exists before you commit to THT — one THT part can add a separate wave or hand-soldering step to the whole board.
OPTO PLUS LED Corp. has designed and manufactured LED displays in Taiwan since 2009. We offer standard SMD and THT LED seven-segment displays,THT LED Alphanumeric Display, THT LED dot-matrix displays, THT LED standard-product-customization and Full-customized THT LED displays. If you have any related requirements, please contact us via Sales@opledtw.com or through our contact form.
FAQ
THT stands for through-hole technology, a method of assembling electronic components onto a printed circuit board (PCB). THT components have metal leads that pass through plated holes in the PCB and are fixed in place with solder.
THT components have a simple structure and, once assembled, withstand harsh conditions such as high temperature and high humidity. Although surface-mount technology (SMT) keeps maturing, THT is still widely used in student electronics labs, small maker projects and products that must tolerate high temperature and humidity.
Common THT components fall into three groups: THT-packaged passive parts such as resistors, capacitors and inductors; THT-packaged ICs such as the DIP (dual in-line package) mentioned in the article; and THT-packaged circuit modules such as LED 7-segment displays or LCD modules with pins.
There are two main methods. The first is connecting directly through the leads: when the circuit is simple, the leads of THT components can be soldered directly, which suits student experiments and small prototype runs. The second is mounting on a PCB, the most common method, using wave soldering for mass production or hand soldering for small batches.
THT goes by several names in different regions: DIP package, because THT ICs have symmetrical leads on two sides and are often called DIP packages or DIP components in Taiwan; components with pins, because THT parts have extended leads; and wave-soldering components, because THT parts are usually assembled by wave soldering.
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