There are several preventive measures to consider in wave soldering. Firstly, it’s essential to improve the PCB manufacturing process to enhance the cleanliness of the hole walls. This includes improving PCB packaging processes and storage conditions. It’s important to minimize dwell time on insertion lines as much as possible. The process from PCB depanelization, component installation to wave soldering should ideally be completed within 24 hours, especially in humid and hot regions. Pre-baking of PCBs before assembly is recommended, and thermal analysis should be conducted after PCB routing and assembly design to avoid the formation of localized heat absorption areas.
Secondly, the temperature at the installation and wave soldering site should be maintained at 24±5°C, with relative humidity not exceeding 65%. It’s crucial to select the correct flux, especially ensuring that the volatility of the solvent used in the flux is appropriate. Too slow or too fast volatilization is not suitable. Reasonable preheating temperature and time selection are also essential. If the temperature is too low or the time is too short, the solvent in the flux is not easy to volatilize, resulting in excessive solvent residue. When entering the wave, the temperature rises sharply, causing the solvent to evaporate violently, forming high-pressure bubbles in the molten solder, which can lead to solder ball formation.
Additionally, it’s advisable to use a combination of radiation and convection preheating methods to accelerate the evaporation of solvents inside the PCB holes. Strengthening flux management to prevent moisture absorption during operation is also important. Control the flux application amount properly—not too much or too little. Excessive flux leads to excessive solvent, which is difficult to volatilize during preheating, while too little flux cannot exert its function properly. Design-wise, it’s best to avoid excessive use of silver-plated pins as they can generate gas during wave soldering. The wave solder shape should ensure that there is no excessive impact movement during solder splash to prevent the formation of small solder beads due to impact.
