Initially, when manually desoldering BGA ICs, many of us may feel apprehensive because we lack an understanding of its soldering process and precautions. Each person may have their own approach to manually desoldering BGAs, but overall, it is important to adhere to scientific soldering standards. Understanding the principles and processes of surface mount soldering for chips can effectively improve the success rate of manual BGA rework.
- Firstly, BGA ICs must be preheated, especially for large-area plastic-packaged BGA ICs, to avoid sudden high temperatures that may cause thermal expansion and damage, or PCB board deformation. Preheating is typically done by raising the hot air nozzle, increasing the distance between the IC, and evenly heating the IC, with the time generally controlled within 10 seconds. If the BGA ICs need to be desoldered from water-damaged phones, the preheating area may be slightly increased to thoroughly remove the IC and PCB moisture. Similarly, when soldering purchased BGA ICs onto the board, attention should be paid to driving out moisture with hot air. Many people overlook this preheating step, which can directly lead to defects in BGA ICs.
- The melting point of rosin is 100 degrees Celsius. Before this temperature, attention should be paid to controlling the maximum heating rate, with Weitek Technology recommending a rate of 40°C/second. During the soldering process, the heating rate should be controlled after adjusting the distance between the nozzle and the IC.
- The melting point of solder is 183 degrees Celsius, but considering the “natural loss” and “heat dissipation” of heat in both production lines and rework, the actual soldering temperature used will be higher. Weitek Technology recommends a reflow soldering temperature of 215-220 degrees Celsius.
When repairing and desoldering BGA chips in mobile phones, it is recommended to use temperatures above 215-220 degrees Celsius, as manual desoldering tends to lose heat more easily compared to wave soldering on production lines. Additionally, different brands of hot air guns have varying airflow and heat, leading to temperature differences. We have used different brands of hot air guns, and temperature adjustment always varies. Sometimes, the temperature for desoldering ICs can reach as high as 300°C, 400°C, or even higher. Moreover, different solder pastes with varying melting points may require different temperatures. Therefore, when performing BGA IC rework, it is necessary to determine the accurate temperature based on individual circumstances.
In conclusion, understanding the principles of BGA IC soldering has a significant impact on the success rate of BGA rework desoldering. Only by understanding the process and principles can you better control the temperature and improve the rework success rate.
