1. **Introduction**

Welding is fundamentally a chemical treatment process. A printed circuit board (PCB) serves as a substrate for circuit elements and devices in electronic products, providing essential electrical connections between them. With the rapid advancement of electronic technology, PCB density is increasing, resulting in more layers. Often, all designs may be correct (e.g., the circuit board is undamaged, and the printed circuit design is flawless); however, issues during the welding process can lead to defects and compromised quality. This negatively impacts the pass rate of the circuit board, which in turn affects the overall reliability of the final product. Therefore, it is crucial to analyze the factors influencing the welding quality of printed circuit boards, investigate the root causes of welding defects, and enhance the overall welding quality of the circuit board.

2. **Reasons for Welding Defects**