Maximum Clamping Force for PCB Thermal Management

When it comes to ensuring optimal contact between a PCB and a heatsink, determining the appropriate clamping force is crucial. Here are some key considerations:

• Compliance: The clamping system should have some flexibility to accommodate dimensional changes caused by temperature variations. This can be achieved through elastic design or the use of compliant thermal pads.
• Minimum Design Pressure: The minimum force required is to overcome any inherent flatness issues in the PCB or constraints imposed by mechanical factors.
• Factors Influencing Maximum Clamping Pressure:
• Mechanical Stress Effects: Changes in component or PCB properties due to stress may impact performance.
• PCB Bending: While maintaining PCB flatness is important, excessive bending stress should be avoided.
• PCB Substrate Creep: To prevent creep, the compressive stress on FR4 substrates should ideally stay below 50MPa.
• Device Package/Die Stress: Guidelines for allowable stress in the device package or die should be considered.
• Solder Joint Stress: Compressive stress on solder joints should be evaluated, especially for parts with large under-package joints.
• If you’re seeking quantitative guidelines or references on this topic, it’s beneficial to explore existing analyses or reliable sources for further insights.