Selective Welding Processes in PCB Fabrication
There are two primary selective welding processes used in PCB fabrication: drag welding and dip welding.
Drag Welding Process
- The drag welding process involves using a small-tip solder wave to weld in tight spaces on a PCB.
- Individual solder joints, pins, and single row pins can undergo drag welding.
- Welding stability is maintained by keeping the inner diameter of the welding nozzle below 6mm.
- Optimal welding quality is achieved by moving the PCB across the solder wave at various speeds and angles.
Advantages of Drag Welding
- Higher heat conversion efficiency compared to dip welding.
- Enhanced stability and reliability due to the prevention of oxidation of solder waves.
- High precision and flexibility in welding electronic components onto PCBs.
Dip Welding Process
- Offers better heat conversion efficiency due to solder solution and PCB board movement.
- Heat for weld joint formation is transferred through the solder wave.
- Requires a solder temperature range of 275℃ to 300℃ and a drag speed of 10mm/s to 25mm/s.
Challenges of Dip Welding
- Longer welding time compared to other processes.
- Lower welding efficiency with increasing number of solder spots.
Immersion Selective Welding System
- Features multiple solder nozzles designed one-to-one with PCB solder spots.
- Output matches traditional wave soldering equipment with lower equipment cost.
- Enables simultaneous fluxing, preheating, and soldering of pending solder joints.
Considerations for Immersion Selective Welding
- Special solder nozzles must be made for different PCBs due to varying solder joint distributions.
- Weld nozzle size should be kept as large as possible for process stability.
Overall, selective welding processes offer unique advantages and challenges in PCB fabrication, catering to different production needs and requirements.
