Mo-TZM and Copper Composite Heat Sinks Offer Superior Thermal Expansion Matching for High-Power Electronics

Why It Matters

Effective thermal management is critical for the reliability and longevity of power electronics. This research presents a novel composite material approach that directly addresses the mismatch in thermal expansion between heat sinks and sensitive semiconductor components, a common failure point in high-power applications.

Key Finding

New heat sinks made from molybdenum or TZM infiltrated with copper have a thermal expansion rate that better matches sensitive semiconductor materials, and they dissipate heat effectively, making them suitable for demanding electronic applications.

Key Findings

• Mo-based heat sinks achieved an improved CTE of 6.6 × 10⁻⁶ K⁻¹, which is closer to that of GaAs (5.7 × 10⁻⁶ K⁻¹) than conventional Cu-Mo-Cu laminates (7.6 × 10⁻⁶ K⁻¹).
• The composite heat sinks exhibited thermal diffusivity within the upper range of commercial laminated heat sinks (≈61 × 10⁶ m²/s).
• Mo microstructures showed resistance to recrystallization up to 1073 K, while TZM showed resistance even at 1373 K, indicating good high-temperature stability.

Research Evidence

Aim: Can a composite heat sink fabricated from laser powder bed fusion of Mo/TZM with copper infiltration achieve a coefficient of thermal expansion (CTE) closer to that of GaAs semiconductors compared to conventional Cu-Mo-Cu laminates, while maintaining competitive thermal diffusivity?

Method: Experimental fabrication and characterization

Procedure: Mo and TZM alloy exoskeletons with honeycomb cavity structures were fabricated using laser powder bed fusion. These structures were then infiltrated with oxygen-free high conductivity copper under an inert atmosphere. The thermal expansion behavior and thermal loading of the base materials and the final composite were evaluated. Microstructural analysis was performed after exposure to elevated temperatures. Thermal diffusivity was measured.

Context: Additive manufacturing for advanced thermal management solutions in power electronics.

Design Principle

Material selection and composite design should prioritize minimizing coefficient of thermal expansion mismatch between joined components to reduce stress and enhance durability.

How to Apply

When designing enclosures or thermal management systems for high-power semiconductors (e.g., in aerospace, high-performance computing, or electric vehicles), investigate the use of additive manufacturing to create composite heat sinks with tailored thermal expansion properties.

Limitations

Hardness of Mo-based heat sinks was reduced at 1373 K. Long-term performance and reliability under various operational stresses were not fully explored.

Student Guide (IB Design Technology)

Simple Explanation: Scientists made a new kind of heat sink using metal powder and copper that fits better with electronic chips, meaning less stress and better performance.

Why This Matters: This research shows how choosing the right materials and manufacturing process can solve a big problem in electronics: heat and the stress it causes. This is important for making devices last longer and work better.

Critical Thinking: While the CTE match is improved, how does the difference in thermal conductivity between Mo/TZM and copper affect the overall heat dissipation pathway and potential for localized hot spots within the composite structure?

IA-Ready Paragraph: The fabrication of Mo-TZM and copper composite heat sinks using laser powder bed fusion demonstrates a novel approach to thermal management. The resulting materials exhibit a coefficient of thermal expansion (CTE) closer to that of semiconductor materials like GaAs, which is crucial for reducing thermal stress and improving the reliability of power electronics. This research provides a strong precedent for exploring advanced material composites in design projects requiring effective thermal dissipation.

Project Tips

• Consider the thermal expansion properties of all materials in your design, especially when they are joined.
• Explore additive manufacturing techniques for creating complex, multi-material components.

How to Use in IA

• This research can inform material selection for a heat sink design, particularly if the design aims to improve thermal management for a specific electronic component.

Examiner Tips

• Demonstrate an understanding of how material properties, such as CTE, directly impact the performance and reliability of a designed product.

Independent Variable: ["Material composition (Mo, TZM, Cu infiltration)","Heat sink structure (honeycomb cavity)"]

Dependent Variable: ["Coefficient of Thermal Expansion (CTE)","Thermal diffusivity","Microstructure stability (recrystallization)","Hardness"]

Controlled Variables: ["Manufacturing process (Laser Powder Bed Fusion)","Infiltration atmosphere (inert)","Testing temperatures","Semiconductor material (GaAs for CTE comparison)"]

Strengths

• Addresses a critical engineering challenge in thermal management.
• Utilizes advanced additive manufacturing techniques.
• Provides quantitative data on material properties and performance.

Critical Questions

• What are the long-term implications of the reduced hardness at higher temperatures for the structural integrity of the heat sink?
• How does the cost and complexity of this additive manufacturing process compare to traditional methods for heat sink production?

Extended Essay Application

• Investigate the feasibility of designing and fabricating a custom heat sink for a specific electronic device using additive manufacturing, focusing on optimizing CTE matching and thermal conductivity.

Source

Laser Powder Bed Fusion Additive Manufacturing of Mo and TZM Exoskeleton with Cu Infiltration for New Heat Sinks Configuration · Advanced Engineering Materials · 2023 · 10.1002/adem.202301409