Introduction to PCB Distortion in PCBA Mass Production:
- PCB distortion in mass production can significantly impact patching and testing, necessitating avoidance measures.
2. Causes of PCB Distortion:
- Raw Material Selection:
- Low T value, especially in paper-based PCBs, can lead to bending due to high processing temperatures.
- Unreasonable PCB Design:
- Uneven component distribution and larger connectors induce excessive thermal stress, causing permanent distortion.
- Design Issues:
- Double-sided PCBs with uneven copper foil distribution may result in uneven shrinkage and deformation.
- Fixture Problems:
- Improper fixture use, especially tight clamps in wave soldering, can lead to PCB expansion and deformation.
- Reflow Soldering Temperature:
- Excessive temperatures during reflow soldering contribute to PCB distortion.
3. Solutions Proposed by Engineers:
- Material Selection:
- Opt for PCBs with high Tg or increase thickness for an optimal aspect ratio if cost and space permit.
- Balanced PCB Design:
- Ensure balanced steel foil area on both sides, cover unused areas with copper in a grid pattern to enhance PCB 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 if slight distortion occurs, use positioning fixtures and heat reset to release stress.
4. 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.
