Main Causes

1. Unreasonable PCB layout design leads to uneven heating on both ends of components;

2. Placement position deviation caused by inaccurate machine calibration;

3. Oxidation and dirt on single-side pads or component pins affect soldering performance;

4. Missing printing and offset solder paste result in uneven solder volume;

5. Too fast heating speed in reflow oven causes inconsistent melting speed of solder paste;

6. Different pad sizes on two sides lead to unbalanced soldering tension.

Practical Improvement Measures

1. Optimize PCB design to ensure same pad size and balanced heat absorption;

2. Calibrate placement machine regularly to improve mounting accuracy;

3. Take good storage measures to prevent oxidation and contamination of boards and components;

4. Inspect stencils frequently to ensure even and complete solder paste printing;

5. Slow down preheating speed inside reflow oven to balance solder melting progress;

6. Adopt standardized components with stable and consistent solderability.

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