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

Technical Documentation & Analysis: Diamond for Advanced Ga₂O₃ Thermal Management

Executive Summary

This research validates the critical role of high-thermal-conductivity diamond in solving the severe self-heating challenges inherent to Gallium Oxide (Ga₂O₃) power devices. The key findings and value proposition are summarized below:

Application Focus: Addresses critical thermal management challenges in high-power, low-loss Ga₂O₃ devices, which suffer from low intrinsic thermal conductivity (10-27 W/m·K).
Proposed Solution: An advanced double-sided cooling flip-chip packaging structure utilizing a diamond layer as a high-flux heat spreader on the top surface.
Material Performance: Simulation utilized diamond with thermal conductivity ($\lambda$) up to 2500 W/m·K, demonstrating its effectiveness in bidirectional heat dissipation.
Thermal Reduction: The diamond layer reduced the maximum chip temperature by 7 °C compared to conventional single-sided flip-chip packaging (103 °C vs. 110 °C) at 3.2 W/mm power density.
High Power Density: The enhanced structure achieved a maximum power density of 6.8 W/mm while maintaining the chip temperature below the 200 °C operational limit.
System Integration: Combining the diamond package with external water cooling further reduced the maximum temperature by 14 °C (down to 186 °C) at 6.8 W/mm, confirming feasibility for high-power applications.

Technical Specifications

The following hard data points were extracted from the simulation results and material parameters, highlighting the performance gains achieved by integrating diamond material.

Parameter	Value	Unit	Context
Diamond Thermal Conductivity ($\lambda$)	Up to 2500	W/m·K	Material used for double-sided cooling
Ga₂O₃ Intrinsic Thermal Conductivity ($\lambda$)	10-27	W/m·K	At room temperature
Baseline Power Density (P)	3.2	W/mm	Initial simulation condition
Max T (Conventional Wire Bonding)	115	°C	At 3.2 W/mm
Max T (Single-Sided Flip-Chip)	110	°C	At 3.2 W/mm
Max T (Double-Sided FC w/ Diamond)	103	°C	At 3.2 W/mm
Temperature Reduction (vs. Single-Sided FC)	7	°C	Thermal benefit of diamond layer
High Power Density Achieved (Max T < 200 °C)	6.8	W/mm	Enhanced double-sided cooling
Max T (6.8 W/mm, w/ Water Cooling)	186	°C	Top surface boundary condition set to 150 °C
Diamond Heat Sink Dimensions	2 x 2 x 0.1	mm³	Simulated diamond layer size
Copper Pillar Radius (r)	20	µm	Flip-chip interconnection
Copper Pillar Height (h)	99	µm	Flip-chip interconnection

Key Methodologies

The thermal performance was validated through detailed simulation models comparing three packaging structures. The advanced double-sided cooling structure relied on precise material selection and dimensional control:

Device Modeling: The simulation utilized a Ga₂O₃ device model with the heat source defined at the active channel layer (200 µm x 5 µm x 0.2 µm).
Baseline Structures: Wire bonding and single-sided flip-chip models were established using standard materials (Al₂O₃ ceramic substrate, Cu base plate, 60Sn-40Pb solder, and epoxy underfill).
Flip-Chip Interconnect: Electrical and thermal connection in the flip-chip models was achieved using high-conductivity copper pillars (r = 20 µm, h = 99 µm).
Diamond Integration: The advanced structure incorporated a layer of high thermal conductivity diamond (simulated $\lambda$ up to 2500 W/m·K) with dimensions of 2 mm x 2 mm x 0.1 mm³ (100 µm thickness) placed on top of the Si substrate for upward heat dissipation.
External Cooling Simulation: To model maximum performance, a boundary temperature condition of 150 °C was applied to the top surface of the diamond layer, simulating the integration of external water-cooling equipment.

6CCVD Solutions & Capabilities

The successful implementation of this advanced double-sided cooling structure hinges on the availability of high-quality, high-purity diamond material with precise dimensional control. 6CCVD is uniquely positioned to supply the required MPCVD diamond components for replicating and extending this research in high-power Ga₂O₃ and other Wide Bandgap (WBG) applications.

Research Requirement	6CCVD Material Solution	Technical Capability Match
High Thermal Conductivity ($\lambda$ up to 2500 W/m·K)	Optical Grade Single Crystal Diamond (SCD)	6CCVD provides high-purity SCD with thermal conductivity consistently exceeding 2000 W/m·K, essential for minimizing thermal boundary resistance (TBR) and maximizing heat flux.
Precise Thickness Control (0.1 mm / 100 µm)	Custom SCD Thickness	We offer precise thickness control for SCD wafers from 0.1 µm up to 500 µm, allowing engineers to optimize the thermal budget and mechanical stability of the heat spreader.
Custom Die Size (2 mm x 2 mm)	Custom Dicing and Dimensions	6CCVD provides custom laser cutting and dicing services to produce diamond plates in any required dimension, from small dies to large Polycrystalline Diamond (PCD) wafers up to 125 mm.
Interface Bonding Preparation (Cu/Solder)	In-House Metalization Services	We offer internal metalization capabilities (Au, Pt, Pd, Ti, W, Cu) necessary for creating robust, low-resistance thermal and electrical interfaces required for flip-chip bonding and integration with Cu pillars and solder layers.
Optimal Surface Finish	Ultra-Low Roughness Polishing	Our SCD material can be polished to achieve surface roughness (Ra) < 1 nm, which is critical for minimizing thermal resistance at the diamond/Ga₂O₃ interface.

Engineering Support

6CCVD’s in-house PhD engineering team specializes in the application of MPCVD diamond for demanding thermal, electronic, and optical systems. We can assist researchers and engineers in selecting the optimal diamond material (SCD vs. PCD) and specifications (thickness, doping, and metalization scheme) required for similar Ga₂O₃ and WBG thermal management projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We offer global shipping (DDU default, DDP available) to ensure rapid delivery of mission-critical materials.

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]