PCB Distortion in PCBA Mass Production: Understanding and Solutions
Causes of PCB Distortion:
- Raw Material Selection: Low T value in paper-based PCBs can cause bending during high processing temperatures.
- Unreasonable PCB Design: Uneven component distribution and large connectors induce thermal stress leading to permanent distortion.
- Design Issues: Uneven copper foil distribution in double-sided PCBs may result in deformation.
- Fixture Problems: Improper fixture use, like tight clamps in wave soldering, can cause PCB expansion and deformation.
- Reflow Soldering Temperature: Excessive temperatures during reflow soldering contribute to PCB distortion.
Solutions Proposed by Engineers:
- Material Selection: Opt for PCBs with high Tg or increase thickness for optimal aspect ratio.
- Balanced PCB Design: Ensure balanced steel foil area on both sides and cover unused areas with copper in a grid pattern for enhanced rigidity.
- Pre-Bake PCB: Pre-bake PCBs before patching at 125℃/4h to minimize distortion risks.
- Fixture Adjustment: Adjust fixtures and clamping distances to accommodate PCB thermal expansion space.
- Temperature Control in Soldering: Lower soldering process temperatures and use positioning fixtures and heat reset to release stress if slight distortion occurs.
Conclusion:
- Engineers propose practical solutions to address PCB distortion issues during PCBA processing, emphasizing material selection, balanced design, pre-baking, fixture adjustments, and temperature control for satisfactory results.
