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.