Simulations of diamond heat spreader for the thermal management of GaN HEMT
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-01-01 |
| Authors | Shirui Pu, Wenbo Luo, Yao Shuai, Chuangui Wu, Wanli Zhang |
| Institutions | State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Diamond Heat Spreaders for GaN HEMT Thermal Management
Section titled âTechnical Documentation & Analysis: Diamond Heat Spreaders for GaN HEMT Thermal ManagementâThis document analyzes the research paper âSimulations of diamond heat spreader for the thermal management of GaN HEMTâ and outlines how 6CCVDâs advanced MPCVD diamond materials and customization capabilities directly support and enable the replication and extension of this critical high-power electronics research.
Executive Summary
Section titled âExecutive SummaryâThe integration of high-thermal-conductivity CVD diamond is essential for managing the extreme heat fluxes generated by AlGaN/GaN High-Electron Mobility Transistors (HEMTs).
- Core Value Proposition: Combining a diamond heat spreader with a liquid-cooled Si microchannel heat sink significantly improves the cooling capability for GaN HEMT hotspots.
- Performance Achievement: Simulation demonstrated that a 200 ”m diamond heat spreader reduced the maximum gate temperature by 20.4% under a 36 W total power load.
- Material Optimization: The heat dissipation capacity of the diamond spreader tends to saturate at thicknesses above 250 ”m, defining an optimal material thickness range for high-flux applications.
- System Optimization: The study confirmed that thinning the underlying Si die (from 400 ”m to 50 ”m) is equally critical, reducing the maximum gate temperature from 124.4 °C to 88.6 °C.
- Methodology: Steady-state finite element analysis (FEA) was used, incorporating temperature-dependent thermal conductivity models for all materials, including diamond (1832 W/mK at 298 K).
- Conclusion: High-quality CVD diamond is confirmed as the superior material for reducing junction temperature and ensuring the stability and efficiency of high-power GaN devices.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the simulation parameters and results, highlighting the critical material requirements for thermal management in GaN HEMT devices.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Thermal Conductivity (T=298 K) | 1832 × (298/T)1.305 | W/mK | Temperature-dependent model used in simulation. |
| Optimal Diamond Spreader Height (h) | 250 - 300 | ”m | Thickness range where cooling performance saturates. |
| Si Die Height (hSi) | 50 - 400 | ”m | Thinning the Si die is crucial for overall thermal path reduction. |
| Maximum Power Load (Ptotal) | 36 | W | Total power applied across six simulated gate heaters. |
| Max Temperature Reduction (200 ”m Diamond) | 20.4 | % | Reduction achieved compared to structure without diamond. |
| Minimum Gate Temperature Achieved | 88.6 | °C | Achieved with 200 ”m diamond and 50 ”m Si die. |
| Au/Sn Solder Thickness (hsolder) | 3 | ”m | Required thickness for bonding the diamond spreader. |
| GaN Layer Thickness (hGaN) | 2 | ”m | Thickness of the active GaN layer. |
| HEMT Die Dimensions (L × W) | 6000 × 7200 | ”m | Dimensions of the simulated Si/spreader/solder stack. |
Key Methodologies
Section titled âKey MethodologiesâThe thermal performance analysis was based on a steady-state finite element simulation model constructed in ANSYS.
- Structure Definition: The cooling structure consisted of a GaN/AlGaN HEMT die, bonded via Sn-based solders to a diamond heat spreader, which was then bonded to a liquid-cooled Si microchannel heat sink.
- Heat Source Modeling: Six tiny heater areas, representing the gate fingers of the HEMT, were used to simulate the concentrated hotspots.
- Power Input: A total power of 36 W was applied simultaneously across the six heaters.
- Thermal Modeling: Temperature-dependent thermal conductivity models were applied to all materials (Diamond, Si, GaN/AlGaN) to accurately capture self-heating effects.
- Cooling Conditions: Simulations were performed at an ambient temperature of 20 °C. The microchannel coolant was 280 K water flowing at 0.2 m/s, operating in the laminar regime.
- Boundary Conditions: The calculation region utilized adiabatic boundary conditions, and radiation heat transfer was ignored.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD specializes in providing the high-quality MPCVD diamond materials and precision engineering required to implement and advance thermal management solutions for high-power devices like GaN HEMTs.
| Research Requirement | 6CCVD Applicable Materials & Services | Technical Advantage for Replication |
|---|---|---|
| High Thermal Conductivity Diamond (Required: > 1800 W/mK) | Optical Grade Single Crystal Diamond (SCD) or High-Purity Polycrystalline Diamond (PCD). | 6CCVD guarantees superior thermal properties, ensuring maximum heat spreading efficiency necessary to achieve the simulated 20%+ temperature reduction. |
| Custom Thickness Control (Required: 50 ”m to 300 ”m) | SCD and PCD Thickness Control (0.1 ”m - 500 ”m). | We provide precision growth and lapping to meet the exact thickness requirements (e.g., 250 ”m) for optimal thermal resistance matching in the HEMT stack. |
| Precision Die Dimensions (Required: 6 mm × 7.2 mm) | Custom Dimensions and Laser Cutting Services. | 6CCVD supplies wafers up to 125 mm (PCD) and offers precision laser cutting to match specific HEMT package footprints, minimizing material waste and ensuring tight tolerances. |
| Low-Resistance Bonding Interface (Au/Sn solder used) | Internal Metalization Services (Ti, Pt, Au, W, Cu). | We offer custom metalization stacks (e.g., Ti/Pt/Au) optimized for low thermal boundary resistance (TBR) bonding using Sn-based solders, critical for high-flux applications. |
| Surface Quality for Integration | Ultra-Low Roughness Polishing (Ra < 1 nm for SCD, Ra < 5 nm for PCD). | A superior surface finish is mandatory for direct bonding and minimizing the thermal impedance introduced by the solder layer (hsolder = 3 ”m). |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD engineering team specializes in optimizing diamond material selection for high-power thermal management applications, including GaN HEMT and RF power amplifier projects. We provide consultation on:
- Selecting the optimal SCD vs. PCD grade based on required thermal conductivity, size, and cost constraints.
- Designing custom metalization schemes to ensure robust, low-TBR bonding to Si, SiC, or active device layers.
- Determining the ideal diamond thickness to balance heat spreading effectiveness against overall package height and cost.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
A diamond heat spreader has been combined with Si microchannel for the improvement of the hotspots cooling capability for GaN high power electronic devices.The effects of the diamond heat spreader and Si die have been simulated using steady model by finite element analysis.It was found that the diamond spreader can reduce the maximal temperature of GaN device.The effect of thickness of Si die on maximum gate temperature will be increases linearly with the increase of total power.These methodology shows promising way to cool AlGaN/GaN HEMTs on Si.