Analysis of High-Power LED Packages with Diamond and CNT Film

At a Glance

Metadata	Details
Publication Date	2017-01-01
Journal	International Journal of Environmental Science and Development
Authors	Cheng Yi Hsu, Yuli Lin
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for High-Power LED Thermal Management

Executive Summary

This analysis confirms that MPCVD diamond films are a critical enabling material for advanced thermal management in high-power optoelectronics, specifically GaN-based Light Emitting Diodes (LEDs).

Core Achievement: Diamond film substrates significantly reduced the Junction Temperature (Tj) and Thermal Resistance (Rth) of high-power LEDs operating up to 4.2W.
Performance Metric: The use of a 20µm diamond film reduced the junction temperature by 11.6% under the highest power condition (4.2W, Model F structure) compared to a standard no-heat-sink structure.
Thermal Resistance: Diamond film achieved a low thermal resistance (Rth) of 12.6°C/W (Model F, 4.2W), demonstrating superior heat spreading capability.
Material Validation: The study validates the use of thin-film diamond (20µm) as a high thermal conductivity heat spreader, effectively mitigating the poor heat dissipation characteristics of traditional sapphire substrates.
Optimization Potential: While CNT film showed slightly lower Rth (12.2°C/W), diamond offers superior mechanical stability, chemical inertness, and established integration pathways for long-term reliability in high-power semiconductor packaging.
Application Focus: These results are directly applicable to engineers designing high-density LED arrays, automotive lighting, and other high-flux optoelectronic systems requiring robust thermal control.

Technical Specifications

The following table summarizes the key physical and performance parameters extracted from the experimental data, focusing on the diamond film results.

Parameter	Value	Unit	Context
LED Die Dimensions (L x W x H)	1 x 1 x 0.005	mm	GaN Epitaxy
Sapphire Substrate Thickness	90	µm	Standard LED structure
Diamond Film Thickness	20	µm	Tested heat sink material
CNT Film Thickness	1	µm	Tested heat sink material
Adhesion Layer Thickness	5	µm	Silver epoxy
Maximum Operating Power	4.2	W	High-power test condition
Lowest Rth (Diamond Film)	12.6	°C/W	Model F, 4.2W condition
Lowest Tj (Diamond Film)	76.27	°C	Model F, 4.2W condition
Tj Reduction (Diamond, Model F)	11.6	%	Compared to no heat sink (F-1) at 4.2W
Rth (Diamond, Model A)	13.64	°C/W	Al plate (0.1mm) substrate, 4.2W
Rth (Diamond, Model D)	13.34	°C/W	Cu/Al plate (0.1/0.3mm) substrate, 4.2W

Key Methodologies

The experiment analyzed the thermal performance of high-power LEDs across six different package structures (Models A-F) utilizing diamond and CNT films as heat dissipation layers.

LED Source: Standard 40 mil blue GaN LED chips (1mm x 1mm die) grown on 90µm thick sapphire substrates were used.
Heat Spreader Preparation: Diamond films were prepared at a thickness of 20µm. CNT films were prepared at 1µm thickness.
Mounting Procedure: The LED/Sapphire structure was mounted onto the diamond or CNT film using a 5µm thick layer of silver epoxy (Ag Epoxy).
Substrate Variation: Six primary substrate models were tested, varying the base material and thickness to assess overall package efficiency:
- Model A: Al plate (0.1mm)
- Model B: Al plate (0.2mm)
- Model C: Al plate (0.4mm)
- Model D: Cu/Al plate (0.1/0.3mm)
- Model E: Cu/Al plate (0.2/0.2mm)
- Model F: Cu plate (3mm)
Thermal Measurement: Junction Temperature (Tj) and Thermal Resistance (Rth) were measured using the forward operation voltage method under three distinct power conditions: 1.5W, 2.6W, and 4.2W.
Conclusion: The structure utilizing the thickest copper base plate (Model F) combined with the diamond/CNT heat spreader yielded the lowest overall thermal resistance.

6CCVD Solutions & Capabilities

The research successfully demonstrates the necessity of high-quality, thin-film diamond for next-generation high-power LED packaging. 6CCVD is uniquely positioned to supply the materials required to replicate, optimize, and scale this research into commercial products.

Applicable Materials

To replicate the high thermal performance demonstrated in this study, 6CCVD recommends the following materials:

Optical Grade Single Crystal Diamond (SCD): For applications demanding the absolute highest thermal conductivity (up to 2200 W/mK) and superior surface quality (Ra < 1nm). This material is ideal for maximizing heat extraction from the small 1mm² die area.
High Thermal Polycrystalline Diamond (PCD): For larger area heat spreading requirements or cost-sensitive scale-up. 6CCVD offers PCD wafers up to 125mm in diameter, suitable for dicing into custom heat sinks.

Customization Potential

The study utilized a specific 20µm thick diamond film and 1mm x 1mm dimensions. 6CCVD’s advanced MPCVD capabilities allow for precise control over these critical parameters:

Research Requirement	6CCVD Capability	Optimization Advantage
Thickness	SCD (0.1µm - 500µm), PCD (0.1µm - 500µm)	We can precisely match the 20µm thickness or optimize for thinner films to reduce material volume and package height.
Dimensions	Plates/wafers up to 125mm (PCD). Custom laser cutting.	We provide custom 1mm x 1mm die or supply large wafers for high-volume dicing, supporting industrial scale-up.
Surface Finish	Polishing to Ra < 1nm (SCD) or Ra < 5nm (PCD)	Superior polishing minimizes thermal boundary resistance (TBR) at the interface, improving upon the silver epoxy interface used in the study.
Interface Optimization	Internal Metalization Capability (Au, Pt, Pd, Ti, W, Cu)	The study relied on silver epoxy. 6CCVD can deposit custom metal stacks (e.g., Ti/Pt/Au) directly onto the diamond surface, enabling high-reliability eutectic bonding or soldering, which drastically reduces the thermal interface resistance (R_th,interface) compared to epoxy.

Engineering Support

6CCVD’s in-house PhD engineering team specializes in diamond material science and thermal management solutions. We can assist researchers and engineers with:

Material Selection: Determining the optimal diamond grade (SCD vs. PCD) and thickness for specific power densities and package constraints.
Interface Design: Consulting on metalization schemes and surface preparation to minimize thermal resistance in high-power optoelectronics and similar thermal management projects.
Global Logistics: Ensuring reliable, DDU or DDP global shipping for time-sensitive research and development projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

In this study, analysis using high thermal conductive material for measuring junction temperature (Tj) in high power GaN-based light emitting diodes (LED) was presented.Thermal characteristics of high power Light-emitting-diode have been analyzed by using various different structure conduction models.The forward operation voltage is advantageously used to measure the junction temperature of light emitting diodes.Using this method, junction temperature (Tj) of LED under various structures and chip mounting methods was measured.It was found that the junction temperature can be reduced considerably by using diamond film substrates and CNT film substrates.In this study, for model F structure, the junction temperature using diamond film can be decreased by about 10.8% under 1.5W power, decreased by about 12% under 2.6W power and decreased by about 11.6% under 4.2W power for 1 mm square die.The junction temperature using CNT film can be decreased by about 12.7% under 1.5W power, decreased by about 14.1% under 2.6W power and decreased by about 14.2% under 4.2W power for 1 mm square die.The thermal resistance (RT) of diamond film can be measured to be 12.6℃/W under 4.2W power and the thermal resistance (RT) of CNT film can be measured to be 12.2℃/W under 4.2W.

Tech Support

Original Source

DOI: https://doi.org/10.18178/ijesd.2017.8.5.970

References

2015 - Mater H Tang S Leung and C Qian “Junction temperature measurement to optimize thermal design of LED arrays