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Electronic manufacturing industry PCB/PCBA knowledge
7 circuit board welding processes and their characteristics

PCB (Printed Circuit Board) is an indispensable component of electronic products. The welding process is a critical step in connecting electronic components to the PCB. With the continuous development of electronic technology, various PCB welding processes have emerged. This article will introduce several main 7 types of PCB circuit board welding processes and their characteristics to help readers better understand and choose the welding method that suits their needs.

Table of Contents

Main 7 types of PCB circuit board welding processes

1. Manual soldering process

Manual soldering, also known as traditional welding, is one of the earliest and most common PCB welding processes. It is manually operated and uses soldering iron heat and solder to connect electronic components to the PCB. The main features of the manual welding process include the following:

1. High flexibility: Manual welding is suitable for small batch production and sample production, and can be quickly adjusted and modified as needed.

2. Relatively low technical requirements: Compared with other advanced welding processes, manual welding has relatively low technical requirements for operators, and non-professionals can also perform simple welding work.

3. Lower cost: Manual welding does not require high-cost automated equipment and only requires simple tools to operate, and the cost is relatively low.

2. Wave soldering process

Wave soldering is a common automated soldering process that uses flowing waves of solder to achieve soldering. Specifically, the PCB will be moved slowly through the conveyor belt, while the wave soldering machine will form a spreading wave of solder over the PCB with a strip of pre-melted solder. As the PCB passes through the wave crest, the solder will weld the components to the PCB through the action of heat and surface tension. The characteristics of the wave soldering process are as follows:

1. Efficiency: Wave soldering is an automated process. Through the rapid operation of the machine, it can achieve high-speed, continuous welding and improve production efficiency.

2. Stable welding quality: Wave soldering has good solder wettability and reliability, and can weld multiple pins at the same time to ensure consistent welding quality.

3. Suitable for mass production: Wave soldering is suitable for large-scale production of electronic products and can complete the welding task quickly and accurately.

3. Surface Mount Technology (SMT)

Surface Mount Technology (SMT) is one of the most advanced and commonly used methods in the current PCB welding process. It replaces traditional plug-in component soldering by soldering components directly to the PCB surface. The main features of SMT are as follows:

1. High integration and small size: SMT components are small in size and have small pin spacing, which enables high integration and small size design, helping to improve the performance and overall efficiency of electronic products.

2. High frequency and large bandwidth: The inductance and capacitance between the pins and pads of SMT components are low, making them suitable for high-frequency and large-bandwidth applications, such as communication equipment, computers, etc.

3. Automated production: The SMT welding process is completed with automated equipment, which has the advantages of efficiency, accuracy, and stability. It is suitable for large-scale production and can significantly improve production efficiency.

4. Reflection welding process

Reflection welding is a welding process based on the principle of heat reflection. It uses mirrors and heat reflection plates to reflect heat energy and realize the welding process. The characteristics of the reflection welding process are as follows:

1. No thermal impact and electrostatic impact: During the reflection welding process, the contact time between components and PCB is short, so it can effectively reduce thermal impact and electrostatic impact, helping to protect the performance and quality of electronic components.

2. Fast welding speed: Reflection welding uses pulse heat energy, and the welding speed is faster, which improves production efficiency and process control stability.

3.Suitable for special components: Reflection welding is suitable for temperature-sensitive components, such as LEDs, photosensitive components, etc., which can avoid damage caused by high temperatures.

5. Lead-free soldering process

Lead-free soldering process is a soldering method introduced to meet environmental protection requirements. Because traditional lead-containing solders may pose potential risks to the environment and human health, lead-free soldering processes are gradually replacing traditional soldering methods. Its main features are as follows:

1. Environmental protection: The lead-free soldering process uses lead-free solder to reduce environmental pollution, comply with environmental protection requirements, and reduce health risks to operators.

2. Stable welding quality: Lead-free solder has good wettability and reliability, and can achieve welding quality comparable to traditional lead-containing soldering.

3. High surface tension control requirements: The surface tension of lead-free solder is relatively large, and the welding process and parameters need to be precisely controlled to ensure welding quality and connection reliability.

6. Reflow Soldering

Reflow Soldering (Hot plate soldering process) is a method of melting solder at a specific temperature and connecting it to components on the PCB. Its main features are as follows:

1. High degree of automation: The hot plate welding process usually uses automated equipment for welding, which can achieve an efficient and precise welding process.

2. Suitable for large-scale production: The hot plate welding process is suitable for large-scale PCB production, enabling batch welding and improving production efficiency.

3. High temperature control accuracy: Hot plate welding requires precise temperature control to ensure that the temperature curve of the welding process meets the requirements and avoid damage to components.

7. Vapor phase relative welding process

Vapor Phase Soldering (VPS) is a method that uses PCB immersed in a liquid with a higher boiling point to achieve soldering. Its main features are as follows:

1. Good temperature uniformity: VPS welds by completely immersing the PCB in the liquid to evenly distribute the welding temperature, which can avoid thermal imbalance and welding defects.

2. Environmental protection: VPS usually uses liquids without hazardous substances as heat transfer media, which meets environmental protection requirements and reduces health risks to operators.

3. Suitable for PCBs with complex structures: The VPS process is suitable for PCBs with complex structures and high-density components, and can achieve high-quality and reliable soldering connections.

8. How to choose the appropriate PCB welding process

How to choose the appropriate PCB welding process?
How to choose the appropriate PCB welding process?

Choosing a suitable PCB welding process requires comprehensive consideration of the following factors:

1. Product requirements: Based on the product’s performance requirements, structural characteristics and usage environment, select a welding process that can meet the requirements.

2. Production scale: According to the size of the production batch and the requirements of the production cycle, select an appropriate automated welding process to improve production efficiency.

3. Cost control: Consider equipment investment, material costs, labor costs and other factors to select an economical and reasonable welding process.

4. Process control requirements: Different welding processes have different requirements for process parameters and environmental conditions, and it is necessary to ensure the feasibility and stability of process control.


The selection of PCB welding process needs to be judged based on specific product needs and production requirements. Manual soldering is suitable for small batch production and sample production; wave soldering is suitable for mass production; SMT is suitable for high integration and small size design; lead-free soldering meets environmental protection requirements; hot plate soldering and VPS are suitable for automated production and complex structure PCBs. Understanding the characteristics and application range of various welding processes will help you choose a process that suits your needs and ensure the improvement of welding quality and production efficiency.

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