Simulation on an Advanced Double-Sided Cooling Flip-Chip Packaging with Diamond Material for Gallium Oxide Devices

At a Glance

Metadata	Details
Publication Date	2024-01-03
Journal	Micromachines
Authors	He Guan, Dong Wang, Wentao Li, Duo Liu, Borui Deng
Institutions	Northwestern Polytechnical University
Citations	6
Analysis	Full AI Review Included

Executive Summary

This study presents a thermal simulation analysis of an advanced double-sided cooling flip-chip (DSFC) packaging structure designed to mitigate the severe self-heating effect in low-thermal-conductivity Gallium Oxide (Ga₂O₃) power devices.

Core Innovation: The DSFC structure enhances conventional flip-chip design by incorporating a high thermal conductivity diamond layer (2500 W/mK) on the top surface of the device, enabling bi-directional heat dissipation.
Thermal Performance Gain (3.2 W/mm): The DSFC structure achieved a maximum chip temperature of 103 °C, representing a 7 °C reduction compared to single-sided cooling flip-chip (110 °C) and a 12 °C reduction compared to traditional wire bonding (115 °C).
Power Density Achievement: The DSFC structure successfully supported a high power density of 6.8 W/mm while keeping the maximum chip temperature below the critical 200 °C limit.
External Cooling Effectiveness: When external water-cooling equipment (modeled at 150 °C boundary) was applied to the DSFC package operating at 6.8 W/mm, the maximum chip temperature was further reduced to 186 °C (a 14 °C improvement).
Conclusion: The diamond-based DSFC packaging structure is confirmed as a highly feasible and practical solution for the thermal management challenges inherent in high-power Ga₂O₃ devices.

Technical Specifications

Parameter	Value	Unit	Context
Ga₂O₃ Thermal Conductivity	10-27	W/mK	Intrinsic material property (Room Temp)
Diamond Thermal Conductivity	2500	W/mK	Material used for top heat sink
Baseline Power Density (P_D)	3.2	W/mm	Standard simulation condition
Max T (Wire Bonding, 3.2 W/mm)	115	°C	Conventional packaging baseline
Max T (Single-Sided FC, 3.2 W/mm)	110	°C	Flip-chip baseline
Max T (Double-Sided FC, 3.2 W/mm)	103	°C	Proposed structure performance
Max Achievable P_D (T_max < 200 °C)	6.8	W/mm	Double-Sided FC structure limit
Max T (DSFC + Water Cooling, 6.8 W/mm)	186	°C	With external cooling (150 °C boundary)
Active Layer Heat Source Size	200 x 5 x 0.2	µm³	Heat generation area
Diamond Heat Sink Dimensions	2 x 2 x 0.1	mm³	Top cooling layer size
Copper Pillar Dimensions	r=20, h=99	µm	Electrical and thermal interconnect
Substrate Material (Bottom)	Al₂O₃	Ceramic	Base plate material
Substrate Material (Top)	Si	Semiconductor	Device layer material

Key Methodologies

The thermal performance of the Ga₂O₃ device packaging was analyzed using detailed thermal simulations based on three structural models:

Device Heat Source Definition:
- The Ga₂O₃ device model was based on a reported structure (Ref. [3]).
- Heat generation was localized to the active channel layer beneath the gate.
- Initial heat dissipation rate was set to 64 mW, corresponding to a power density of 3.2 W/mm.
Baseline Model Simulation:
- Wire Bonding (WB): Heat dissipation primarily occurs downward through the Al₂O₃ ceramic substrate and Cu base plate.
- Single-Sided Flip-Chip (SSFC): The device is inverted, and heat is transferred downward through copper pillars (r=20 µm, h=99 µm) and underfill epoxy to the Cu base plate.
Advanced Double-Sided Cooling (DSFC) Implementation:
- The SSFC structure was modified by adding a layer of C-Diamond material (2 x 2 x 0.1 mm³, 2500 W/mK) on top of the Si substrate.
- This created two primary heat dissipation paths: downward (via copper pillars) and upward (via the Si substrate and diamond layer).
High Power Density Testing:
- The heat source power was increased until the maximum chip temperature reached 200 °C, establishing the maximum achievable power density (6.8 W/mm) for the DSFC structure without external cooling.
External Cooling Integration:
- To simulate practical high-power operation, external water-cooling equipment was modeled.
- A fixed boundary temperature condition of 150 °C was applied to the top surface of the C-Diamond heat sink layer.
- The simulation was run at the high power density of 6.8 W/mm to quantify the temperature reduction achieved by the combined DSFC and external cooling system.

Commercial Applications

The enhanced thermal management provided by the diamond-based double-sided cooling flip-chip packaging is critical for realizing the full potential of Ga₂O₃ in high-performance power applications.

High-Voltage Power Conversion:
- Used in high-efficiency DC-DC converters and AC-DC rectifiers where Ga₂O₃’s large band gap and high breakdown field strength are leveraged.
- Essential for minimizing thermal runaway in high-voltage switching modules.
Electric Vehicle (EV) Powertrains:
- Enables smaller, lighter, and more reliable power modules (inverters, onboard chargers) by allowing higher power density operation without exceeding thermal limits.
Renewable Energy Grid Integration:
- High-power, low-loss devices required for efficient power management in solar and wind farm inverters connecting to the electrical grid.
Aerospace and Industrial Motor Drives:
- Applications demanding extreme reliability and high thermal stability under continuous high-power cycling, benefiting from the 12 °C reduction in operating temperature.
Advanced Packaging Solutions:
- The methodology validates diamond material integration as a viable, high-performance thermal interface for next-generation wide-band-gap semiconductors (GaN, SiC, Ga₂O₃).

View Original Abstract

Gallium oxide (Ga2O3) devices have shown remarkable potential for high-voltage, high-power, and low-loss power applications. However, thermal management of packaging for Ga2O3 devices becomes challenging due to the significant self-heating effect. In this paper, an advanced double-sided cooling flip-chip packaging structure for Ga2O3 devices was proposed and the overall packaging of Ga2O3 chips was researched by simulation in detail. The advanced double-sided cooling flip-chip packaging structure was formed by adding a layer of diamond material on top of the device based on the single-sided flip-chip structure. With a power density of 3.2 W/mm, it was observed that the maximum temperature of the Ga2O3 chip with the advanced double-sided cooling flip-chip packaging structure was 103 °C. Compared with traditional wire bonding packaging and single-sided cooling flip-chip packaging, the maximum temperature was reduced by about 12 °C and 7 °C, respectively. When the maximum temperature of the chip was controlled at 200 °C, the Ga2O3 chip with double-sided cooling packaging could reach a power density of 6.8 W/mm. Finally, by equipping the top of the package with additional water-cooling equipment, the maximum temperature was reduced to 186 °C. These findings highlight the effectiveness of the proposed flip-chip design with double-sided cooling in enhancing the heat dissipation capability of Ga2O3 chips, suggesting promising prospects for this advanced packaging structure.

Tech Support

Original Source

DOI: https://doi.org/10.3390/mi15010098

References

2012 - Gallium oxide (Ga2O3) metal-semiconductor field-effect transistors on single-crystal β- Ga2O3 (010) substrates [Crossref]
2013 - Depletion-mode Ga2O3 metal-oxide-semiconductor field-effect transistors on β- Ga2O3 (010) substrates and temperature dependence of their device characteristics [Crossref]
2016 - Field-plated Ga2O3 MOSFETs with a breakdown voltage of over 750 V [Crossref]
2018 - A review of Ga2O3 materials, processing, and devices [Crossref]
2020 - Vertical β- Ga2O3 power transistors: A review [Crossref]
2017 - High-Performance Depletion/Enhancement-ode β- Ga2O3 on Insulator (GOOI) Field-Effect Transistors with Record Drain Currents of 600/450 mA/mm [Crossref]
2018 - Recessed-Gate Enhancement-Mode β- Ga2O3 MOSFETs [Crossref]
2017 - β- Ga2O3 MOSFETs for Radio Frequency Operation [Crossref]
2020 - Progress of ultra-wide bandgap Ga2O3 semiconductor materials in power MOSFETs [Crossref]
2020 - Enhancement-Mode β- Ga2O3 Current Aperture Vertical MOSFETs with N-Ion-Implanted Blocker [Crossref]