Common problems and solutions in reflow soldering process

Date：2024-04-07 15:17:41Views：45

Reflow soldering is a common surface mount technology widely used in the electronic manufacturing industry. In the reflow soldering process, there are often some problems, such as poor solder joints, component damage, etc., which may affect product quality and production efficiency. This article will introduce common problems in reflow soldering technology, their causes, and solutions to help readers better understand and respond to these problems.

1、 Poor welding connections

1. Problem description: Poor connection after welding, such as cold welding, broken welding, missed welding, etc.

2. Possible reasons:

a. Improper temperature: Welding temperatures that are too high or too low can lead to poor welding.

b. Insufficient welding time: A short welding time may result in insufficient welding stability.

c. Poor solder paste quality: Using low-quality solder paste can affect the welding quality.

3. Solution:

a. Ensure that the welding temperature and time comply with the welding specifications.

b. Use high-quality solder paste and ensure that the storage and use of solder paste meet the requirements.

2、 Welding defects

4. Problem description: Welding defects such as incomplete solder joints, solder spatter, and weld scars occur after welding.

5. Possible reasons:

a. PCB surface contamination: Contaminants may interfere with the welding process, leading to welding defects.

b. Uneven application of solder paste: Uneven distribution of solder paste may lead to welding defects.

c. Poor ventilation: Poor ventilation may lead to welding defects, such as solder spatter.

6. Solution:

a. Keep the welding environment clean and ensure that the PCB surface is free of contaminants.

b. Use precise solder paste application technology to ensure uniform coverage of solder joints.

c. Provide good ventilation conditions to reduce the possibility of welding defects.

3、 Component damage or deformation

7. Problem description: During the welding process, components may be damaged or deformed.

8. Possible reasons:

a. Excessive temperature: Excessive welding temperature may cause component damage or deformation.

b. Thermal stress: Temperature changes during the welding process may cause thermal stress on components.

c. Component quality issue: Low quality components may be more susceptible to the impact of welding processes.

9. Solution:

a. Ensure that the welding temperature meets the specifications of the components and avoid excessive temperatures.

b. Optimize the welding process to reduce the impact of temperature changes on components.

c. Choose high-quality components to increase the reliability of the welding process.

4、 Deviation during welding process

10. Problem description: During the welding process, there are issues such as solder joint displacement and component displacement.

11. Possible reasons:

a. Equipment calibration issue: Improper calibration of the equipment may lead to welding deviations.

b. PCB design issue: Improper PCB design may lead to offset of welding positions.

12. Solution:

a. Regularly calibrate reflow soldering equipment to ensure its stability and accuracy.

b. During the PCB design phase, consider the welding position and direction, and plan the welding layout reasonably.

5、 Special issues with lead-free welding

13. Problem description: When using lead-free solder paste for welding, unstable welding quality may occur.

14. Possible reasons:

a. Improper temperature curve adjustment: Lead free welding requires high welding temperature curve control.

b. Differences in the characteristics of solder alloys: Compared with traditional lead containing solder, lead-free solder has different characteristics.

15. Solution:

a. Optimize the welding temperature curve to ensure stable welding quality in response to lead-free welding requirements.

b. Select suitable lead-free soldering alloys and adjust process parameters according to their characteristics.

When using reflow soldering technology, the following common problems may be encountered:

1. Tin ball: Tin ball refers to the adverse phenomenon formed during the welding process, which is the appearance of small balls of solder on the surface of the solder joint. This is usually caused by high welding temperature, long welding time, or unreasonable welding area design.

Solution: Adjust the welding temperature and time to ensure that the welding parameters meet the requirements; Check the design of the welding area to ensure a reasonable layout of the welding points.

2. Cold welding: Cold welding refers to the welding point not reaching a sufficient melting state, resulting in an unstable connection of the welding point. This may be caused by insufficient welding temperature, insufficient welding time, or improper welding area design.

Solution: Increase the welding temperature and time to ensure complete melting of the solder joints; Check the design of the welding area to ensure good contact between the welding points and the components.

3. Tin connection phenomenon: Tin connection phenomenon refers to the molten solder bridge formed between two or more adjacent solder joints. This is usually caused by high welding temperature, long welding time, or unreasonable welding area design.

Solution: Reduce the welding temperature and time to ensure that there is no excessive melting between the welding points; Check the design of the welding area to ensure that the layout of the welding points is reasonable.

4. Welding offset: Welding offset refers to a certain degree of error between the welding position and the predetermined position. This may be caused by issues with welding equipment or fixtures.

Solution: Check the welding equipment and fixtures to ensure their stability and accuracy; Adjust welding parameters and processes to ensure the accuracy of welding positions.

When solving the above problems, welding quality can be improved by optimizing welding parameters, improving processes, optimizing designs, and other methods. Meanwhile, strict quality control and testing are also important means to ensure welding quality.

Reflow soldering is a commonly used welding process in surface assembly technology, but it may encounter some common problems during use. These issues include poor welding connections, welding defects, component damage or deformation, deviations during the welding process, and special issues with lead-free welding. Understanding possible causes and adopting corresponding solutions can help us improve welding quality, ensure the reliability and stability of welding processes. In practical applications, reasonable setting of welding parameters, control of welding environment, and selection of high-quality materials and equipment are crucial for solving welding problems.