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- April 30, 2023
- PCB knowledge
- (0)
- 06 mins
Through-hole technology – a comprehensive guide for the PCB industry
In the ever-evolving world of electronics, printed circuit boards (PCBs) play a crucial role. PCB assembly techniques have advanced significantly, offering various options for manufacturers.
One such technique is through-hole technology (THT), which has been used for decades and is a popular choice.
This article will explore through-hole technology, its components, the manufacturing process, advantages, disadvantages, and applications in the industry.
What is through-hole technology?
Through-hole technology (THT) refers to a method employed in the assembly of printed circuit board (PCB). This technique involves mounting components by placing their leads into holes on the PCB and subsequently soldering them to corresponding pads on the opposite side of the board. This method ensures a secure mechanical and electrical connection, making it a popular choice in the PCB industry.
What are through-hole components?
Through-hole components are electronic elements specifically created for compatibility with through-hole technology. These components feature extended leads that can be easily inserted into a PCB’s holes and securely soldered to ensure proper connection. Examples of through-hole components include resistors, capacitors, diodes, and integrated circuits.
What is the through-hole technology manufacturing process?
The through-hole technology manufacturing process involves several steps:
1. Drilling
The PCB undergoes a drilling procedure to create holes, which serve as insertion points for the leads of through-hole components.
The size and placement of these holes depend on the component specifications and the PCB layout.
2. Component placement
Through-hole components are manually or automatically placed on the PCB, with their leads inserted into the corresponding holes. Automatic insertion machines are often used for high-volume production.
3. Soldering
After inserting the leads into the holes, they are soldered to the corresponding pads on the reverse side of the PCB, establishing a robust electrical and mechanical bond. Soldering methods used in THT include wave soldering and selective soldering.
4. Cleaning
The assembled PCB is cleaned to remove any flux residue from the soldering process, which could cause short circuits or other issues.
5. Inspection and testing
Upon completion of the PCB assembly, quality control measures are employed, utilizing visual assessment, automated optical inspection, and X-ray inspection methods to ensure the highest standards of quality. It is then tested for functionality, ensuring all components and connections work as intended.
Advantages and disadvantages of through-hole technology
This section will discuss the advantages and disadvantages of through-hole technology, which can help decide whether THT is the right choice for their specific application.
Advantages
- THT provides a robust mechanical bond, making it suitable for components exposed to stress or vibrations, such as aerospace and defense electronics.
- Through-hole components are easier to insert, remove, and replace, which is beneficial during the prototyping phase or when modifications and repairs are needed.
- THT can accommodate larger components and is ideal for high-power circuits, as it can handle higher current levels than surface-mount technology (SMT).
Disadvantages
- THT requires more space on the PCB, resulting in larger and heavier boards than SMT technology.
- Through-hole assembly is slower and more labor-intensive, leading to higher production costs.
- The need for space around each hole limits component density, making THT less suitable for compact and miniaturized designs.
What is through-hole technology used for?
Through-hole technology finds use in numerous applications due to its distinct advantages. Some of the common uses for through-hole technology include:
Aerospace and defense electronics:
Durability and reliability are critical in these applications. The robust mechanical connections created by THT make it a preferred choice for electronic devices exposed to harsh conditions, extreme temperature fluctuations, and persistent vibrations.
Power supplies and high-power circuits:
Through-hole technology’s ability to handle high current levels makes it suitable for power supplies, inverters, converters, and other high-power circuitry. The larger components and robust connections ensure reliable performance in these demanding applications.
Vintage electronics and hobbyist projects:
THT remains popular among enthusiasts who restore or create vintage electronics, as it allows for easy modifications and repairs. Hobbyists often prefer through-hole components for their DIY projects since they can be more easily handled and soldered than surface-mount components.
Industrial and automotive electronics:
For industrial control systems, heavy machinery, and automotive electronics, the robustness and reliability provided by THT can be essential. The strong mechanical connections ensure that components stay in place even under significant vibrations or temperature fluctuations.
Test and measurement equipment:
Precision tests and measurement equipment, such as oscilloscopes and signal analyzers, can benefit from the reliability and ease of repair offered by through-hole technology. The strong connections help ensure the accuracy and stability of these devices.
Audio equipment:
High-quality audio equipment, like amplifiers and mixers, often uses through-hole components due to their reliability and ease of maintenance. THT can handle higher power levels, essential for some audio applications.
What is an example of through-hole technology?
An example of through-hole technology is the assembly of a power amplifier circuit. The circuit contains large capacitors, transformers, high-power transistors, and all through-hole components.
Through-hole technology delivers the necessary mechanical durability and electrical connectivity needed for high-power applications, making it a reliable choice in these high-power demanding applications.
What is the difference between a through-hole vs. blind hole?
Before diving into the comparison table, it’s essential to understand the key differences between through-holes and blind holes in PCB design.
Through-holes are drilled through the board, connecting the top and bottom layers.
In contrast, blind holes are partially drilled through the board, connecting specific layers without penetrating the entire board.
This distinction impacts thermal management, routing complexity, and cost. The following table summarizes the main differences between through-hole and blind holes:
| Feature | Through-Hole | Blind Hole |
| Hole Depth | Goes through the entire board | Partially drilled through the board |
| Connection Type | Connects top and bottom layers of the PCB | Connects specific layers without penetrating the entire board |
| Usage | Used for through-hole components in PCB assembly | Primarily used for multilayer PCB to optimize space and routing efficiency |
| Thermal Management | Conducts heat through the entire PCB, allowing for some heat dissipation | May provide better thermal management by isolating heat between specific layers |
| Routing Complexity | May require additional routing layers for complex designs | Can simplify routing in complex multilayer PCB designs by connecting specific layers only |
| Cost | Generally less expensive due to simpler drilling process | Can be more expensive due to the precision required in drilling and plating blind holes |
Understanding the differences between through-hole and blind holes can help PCB designers make informed decisions about the best approach to optimize space, routing efficiency, and thermal management in their designs.
What is the difference between SMT and through-hole technology?
Surface-mount technology (SMT) and through-hole technology (THT) serve as common methods for assembling PCBs.
SMT involves attaching components to the board’s surface and securing them with solder, THT, as previously described, involves inserting component leads through holes in the board and soldering them on the opposite side.
Here are some key differences between the two technologies:
| Feature | Surface-Mount Technology (SMT) | Through-Hole Technology (THT) |
| Speed and Cost | Faster production, lower cost | Slower production, higher cost |
| Component Size and Density | Smaller components, higher density | Larger components, lower density |
| Mechanical Strength | Less robust mechanical bonds | Stronger mechanical bonds |
| Prototyping and Repair | Challenging to modify or repair | Easier to prototype, modify, and repair |
| Applications | Suitable for compact and miniaturized designs | Ideal for high-power circuits and components exposed to stress or vibrations |
By considering the differences between SMT and THT, manufacturers can choose the most appropriate assembly method for their specific applications, balancing production speed, cost, component size and density, mechanical strength, and ease of prototyping and repair.
What is through-hole technology?
Through-hole technology (THT) refers to a method employed in the assembly of printed circuit boards (PCBs). This technique involves mounting components by placing their leads into holes on the PCB and subsequently soldering them to corresponding pads on the opposite side of the board.
What are through-hole components?
Through-hole components are electronic elements specifically created for compatibility with through-hole technology. Examples of through-hole components include resistors, capacitors, diodes, and integrated circuits.
What is through-hole technology used for?
- Aerospace and defense electronics
- Power supplies and high-power circuits
- Vintage electronics and hobbyist projects
- Industrial and automotive electronics
- Test and measurement equipment
- Audio equipment
Conclusion
Through-hole technology remains valuable in the PCB industry for its mechanical strength and suitability for high-power applications. While surface-mount technology has become more popular due to its speed and cost advantages, THT is preferred for specific applications, such as aerospace and defense electronics or hobbyist projects. Understanding the advantages and disadvantages of THT can help manufacturers make informed decisions about the right assembly method for their products.
