SPRADB7 September   2023 AM2431 , AM2432 , AM2434 , AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1 , AM2732 , AM2732-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 How to Use This Application Note
    2. 1.2 Glossary
  5. 2Thermal Resistance Overview
    1. 2.1 Junction Vs. Ambient Temperature
    2. 2.2 Package Defined Thermal Resistance Characteristics
    3. 2.3 Board Defined Thermal Resistances
  6. 3Board Design Choices that Affect Thermal Performance
    1. 3.1 Thermal Vias
    2. 3.2 Board Size
    3. 3.3 Air Flow, Heat Sinking, and Enclosures
    4. 3.4 Copper Thickness
    5. 3.5 Relative Position of Heat Emitters
    6. 3.6 Layer Count
    7. 3.7 Breaks in Thermal Pathing
  7. 4Thermal Design Best Practices Review
  8. 5AM263x EVM Thermal Comparison with Data
    1. 5.1 Test Setup and Materials
    2. 5.2 Measurement Logging Software
    3. 5.3 AM263x EVM Comparison
    4. 5.4 Measurement Results
      1. 5.4.1 Lid Temperature Readings
      2. 5.4.2 Power Readings over Temperature
      3. 5.4.3 Calculated Thermal Resistance Values
      4. 5.4.4 Recorded Junction and Ambient Temperatures
      5. 5.4.5 Calculated Junction Temperature at Ambient Temperature Extremes
  9. 6Using the Thermal Model
  10. 7References

3.4 Copper Thickness

The copper thickness is important for thermal performance as the ground copper pours are responsible for dispersing the heat that is traveling from the thermal vias. Copper thickness is tied to the copper weight per square foot. Typically, PCBs will have either 0.5 oz/sq ft or 1.0 oz/sq ft.

1 λ ( C u ) ( L e n g t h ) W i d t h * T h i c k n e s s = R Θ ( C o p p e r   l a y e r )

Where λ(Cu) is the conductivity of copper or 4 Watts per meter-kelvin, length and width refers to the length and width of the copper plane.

For best thermal performance:

  • Maximize the area of each copper layer
  • Use heavier copper layers
Table 3-5 AM263x EVM Copper Thickness Comparison
Measurement TMDSCNCD263 LP-AM263
Ground layer copper thickness 1.26 mil 1.26 mil
Copper weight 1 oz/sq ft 1 oz/sq ft