1. **Inappropriate preheating temperature.** A temperature that is too low can lead to poor flux activation or insufficient heating due to PCB design, resulting in inadequate solder melting. This impairs the wettability and fluidity of the solder, leading to bridging between adjacent solder joints.
2. **Flux preheating temperature is too high or too low.** The optimal temperature for flux preheating is generally between 100°C and 110°C. If the preheating is too low, the flux will not activate properly. Conversely, if the preheating is too high, the flux can evaporate, leading to solder bridging.
3. **Improper use or insufficient application of flux.** When no flux is used, or if the flux is applied unevenly or in insufficient quantities, the surface tension of the molten solder is not properly managed, which can result in solder bridging.
4. Check the temperature of the tin furnace and maintain it around 265 degrees Celsius. Use a thermometer to measure the peak temperature when the peak is reached, as the temperature sensor might be located at the bottom or other parts of the furnace. Inadequate preheating temperature can prevent the component from reaching the desired temperature. During soldering, the large amount of heat absorbed by the component can lead to poor tin dragging and continuous solder formation. This issue might also be due to a low furnace temperature or excessive soldering speed.
5. Use the correct technique when hand-dipping tin.
6. Regularly check and analyze the tin composition. If the copper or other metal content exceeds the standard, it may affect the flowability of the tin, leading to tin bridging.
7. Impurities in the solder that exceed acceptable levels can alter its characteristics, degrading its wettability and fluidity. For example, if antimony content exceeds 1.0%, arsenic exceeds 0.2%, or separation exceeds 0.15%, the solder fluidity can decrease by 25%, and arsenic content below 0.005% can lead to dewetting.
8. Check the orbital angle of the wave soldering process. An angle of 7 degrees is generally suitable; if the angle is too flat, it may cause tin to hang.
9. PCB board deformation can cause inconsistent pressure wave depths at different locations (left, middle, and right) on the PCB. This inconsistency can result in uneven tin flow and an increased risk of bridging in areas with deeper tin deposits.
10. Poor design of ICs and power strips can create issues, especially if IC pin spacing on all sides is less than 0.4mm and lacks an inclined angle for board entry.
11. PCB board sinking and deformation during heating can lead to continuous tin flow.
12. The soldering angle of the PCB board affects the likelihood of solder joints being coplanar when separated from the wave crest. A larger angle generally reduces the probability of bridging. Leaded soldering angles are typically adjustable between 4° and 9°, while lead-free soldering angles range from 4° to 6°, depending on the PCB board design. Note that in large-angle soldering, insufficient tin coverage at the front end of the PCB may occur. If this happens, consider reducing the soldering angle.
13. Absence of a solder resist dam between the circuit board pads, or a design defect where the solder resist dam/bridge is partially or entirely missing, can lead to solder bridging after solder paste printing.
2. **Flux preheating temperature is too high or too low.** The optimal temperature for flux preheating is generally between 100°C and 110°C. If the preheating is too low, the flux will not activate properly. Conversely, if the preheating is too high, the flux can evaporate, leading to solder bridging.
3. **Improper use or insufficient application of flux.** When no flux is used, or if the flux is applied unevenly or in insufficient quantities, the surface tension of the molten solder is not properly managed, which can result in solder bridging.
4. Check the temperature of the tin furnace and maintain it around 265 degrees Celsius. Use a thermometer to measure the peak temperature when the peak is reached, as the temperature sensor might be located at the bottom or other parts of the furnace. Inadequate preheating temperature can prevent the component from reaching the desired temperature. During soldering, the large amount of heat absorbed by the component can lead to poor tin dragging and continuous solder formation. This issue might also be due to a low furnace temperature or excessive soldering speed.
5. Use the correct technique when hand-dipping tin.
6. Regularly check and analyze the tin composition. If the copper or other metal content exceeds the standard, it may affect the flowability of the tin, leading to tin bridging.
7. Impurities in the solder that exceed acceptable levels can alter its characteristics, degrading its wettability and fluidity. For example, if antimony content exceeds 1.0%, arsenic exceeds 0.2%, or separation exceeds 0.15%, the solder fluidity can decrease by 25%, and arsenic content below 0.005% can lead to dewetting.
8. Check the orbital angle of the wave soldering process. An angle of 7 degrees is generally suitable; if the angle is too flat, it may cause tin to hang.
9. PCB board deformation can cause inconsistent pressure wave depths at different locations (left, middle, and right) on the PCB. This inconsistency can result in uneven tin flow and an increased risk of bridging in areas with deeper tin deposits.
10. Poor design of ICs and power strips can create issues, especially if IC pin spacing on all sides is less than 0.4mm and lacks an inclined angle for board entry.
11. PCB board sinking and deformation during heating can lead to continuous tin flow.
12. The soldering angle of the PCB board affects the likelihood of solder joints being coplanar when separated from the wave crest. A larger angle generally reduces the probability of bridging. Leaded soldering angles are typically adjustable between 4° and 9°, while lead-free soldering angles range from 4° to 6°, depending on the PCB board design. Note that in large-angle soldering, insufficient tin coverage at the front end of the PCB may occur. If this happens, consider reducing the soldering angle.
13. Absence of a solder resist dam between the circuit board pads, or a design defect where the solder resist dam/bridge is partially or entirely missing, can lead to solder bridging after solder paste printing.
