Soldering is a crucial process for securing components to printed circuit boards (PCBs). It impacts the quality and performance of the PCB. In PCB manufacturing plants, workers operate soldering machines and inspect the soldering after completion using AOI machines or X-ray inspection machines to avoid soldering problems on finished PCBA boards.

　　For electronics manufacturers or beginners, manual soldering has always been considered an essential skill. However, problems can occur even with expert or automated machine soldering. This article is a guide to PCB soldering.

　　1. Solder bridges: A solder bridge is an unnecessary extra solder connection between adjacent solder joints, which can cause short circuits. To avoid solder bridges, it is crucial to choose the right soldering tools (such as a soldering station and soldering tip) for the task, with the tip size matching the solder joint size. During soldering, control the amount of solder used to prevent unnecessary connections between adjacent solder joints. After soldering, carefully inspect with a magnifying glass or microscope to ensure there are no solder bridges.

　　2. Cold solder joints: A cold solder joint occurs when the solder fails to fully melt and form a solid connection with the solder joint. This is usually caused by impure solder, insufficient soldering temperature, or too short a soldering time. To prevent cold solder joints, use high-quality solder and ensure the soldering temperature is sufficient. In addition, maintain sufficient soldering time to allow the solder to fully melt and form a stable connection with the solder joint.

　　3. Excess solder: Using too much solder not only wastes material but also results in excessively large solder joints, affecting the layout and aesthetics of the circuit board. Excess solder can also mask potential problems such as dry solder joints or cold solder joints. Therefore, it is crucial to control the amount of solder used during soldering, ensuring that the solder joints are sufficient but not excessive.

　　4. Insufficient solder: Insufficient solder can lead to weak joints that are prone to falling off or breaking. To avoid this, ensure that sufficient solder is used during soldering to form a strong joint. Also, pay attention to the soldering time to avoid insufficient soldering time, which prevents the solder from fully melting.

　　5. Heat damage: Excessive soldering temperature or prolonged soldering time can cause heat damage to the circuit board or components. To prevent this, use soldering tools with temperature control and select the appropriate soldering temperature according to the type of component and circuit board. Avoid staying in the same position for too long during soldering to minimize the risk of heat damage.

　　6. Improper soldering order: Improper soldering order can lead to solder bridges or component displacement. To ensure soldering quality, follow a certain soldering order, usually starting with low, heat-resistant components and then moving to higher, less heat-resistant components. This helps reduce interference and damage during the soldering process.

　　7. Too dirty workspace: Dust, oil, and other contaminants in the workspace can adhere to the solder joints, affecting the soldering quality. Therefore, the workspace should be kept clean and tidy, and the soldering station and tools should be cleaned regularly. Before soldering, ensure that the circuit board and components are clean to prevent contaminants from affecting the soldering quality.

　　8. Improper component placement: Improper component placement can make soldering difficult or result in poor soldering quality. When placing components, ensure that they are correctly aligned and positioned, avoiding problems such as tilting or misalignment. For small components, use tools such as tweezers to assist in placement to ensure stability and accuracy.

　　9. Improper circuit board handling: Improper handling of the circuit board during soldering can cause solder joints to break or components to fall off. Avoid excessive bending or twisting of the circuit board to prevent such damage. After soldering, store the circuit board properly to prevent it from being physically damaged or chemically corroded.

　　10. Lack of inspection: Failure to conduct necessary inspections may lead to overlooking potential problems, thus affecting the final quality of the circuit board. Therefore, after soldering, thoroughly inspect the circuit board, including the appearance and connections of the solder joints. Use a magnifying glass or microscope for detailed inspection to ensure that each solder joint meets the requirements.

　　 Frequently Asked Questions (FAQ)

　　1. What are the main causes of cold solder joints? Cold solder joints are mainly caused by insufficient heat transfer during soldering. This may be due to an unsuitable soldering iron, improper heating, or contamination of the soldering surface.

　　2. How to prevent tombstoning when soldering surface mount devices? To prevent tombstoning, ensure adequate solder paste or solder deposition on the component pads, adjust the reflow profile or soldering iron temperature, consider using solder paste with a higher metal content, and ensure that the component pad size is suitable for the component size.

　　3. What is the best way to remove solder bridges? The recommended method for removing solder bridges is to use solder wick or solder sucker. These materials can absorb and remove excess solder, allowing you to eliminate unintended connections between adjacent pads or traces.

　　4. Can overheating components during soldering cause permanent damage? Yes, overheating can cause permanent damage to sensitive electronic components. Overheating can lead to physical damage, performance degradation, or premature component failure. It is essential to use the appropriate soldering temperature and heat carefully to prevent overheating.

　　5. Why is it important to clean flux residue after soldering? Excessive flux residue on the PCB can lead to corrosion, short circuits, or insulation breakdown, affecting the reliability and performance of the circuit. Proper cleaning with a suitable flux remover or isopropyl alcohol is crucial to ensure long-term durability and functionality.

　　Manual soldering is a key skill in the electronics field, and mastering it requires practice, patience, and attention to detail. By understanding and avoiding these common problems in manual PCB soldering, you can achieve reliable and high-quality solder joints, ensuring the proper function and lifespan of your electronics projects. Remember to follow best practices, use the correct tools and techniques, and prioritize safety throughout the soldering process.