Next Generation High Powered RF and Optical Packages
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2023-10-17 |
| Journal | IMAPSource Proceedings |
| Authors | Ramesh Kothandapani, Tan Sin Li, Tee Zhen Wei, Noel DeLeon, Chen Wang |
| Institutions | Materion (United Kingdom) |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Next Generation High Powered RF and Optical Packages
Section titled āTechnical Documentation & Analysis: Next Generation High Powered RF and Optical PackagesāExecutive Summary
Section titled āExecutive SummaryāThis analysis confirms that MPCVD diamond is the critical enabling material for next-generation high-power RF (GaN/GaAs) and Photonic packaging, directly addressing severe thermal management challenges.
- Thermal Superiority: The research identifies diamond as the benchmark thermal spreader material, offering a Thermal Conductivity (TC) of 1500 W/(mĀ·K), significantly exceeding traditional ceramics (AlN: 200 W/(mĀ·K), SiC: 430 W/(mĀ·K)).
- CTE Matching: Diamond provides an ideal Coefficient of Thermal Expansion (CTE) of 1.4 ppm/K, crucial for reliable, high-shear-strength bonding to high-power semiconductors like GaN (3.2 ppm/K).
- Packaging Requirements: High-reliability GenPackā¢ packages require organic-free, high-melting-temperature brazing, custom electrical circuits, and metal-filled vias to ensure low thermal impedance and high RF performance.
- Performance Validation: Package assemblies demonstrated robust mechanical integrity, maintaining > 100 KgF shear strength even after 1000 temperature cycles, validating the use of high-TC, CTE-matched materials.
- 6CCVD Value Proposition: 6CCVD specializes in the custom fabrication of high-purity SCD and PCD diamond wafers, offering the precise dimensions, metalization schemes (e.g., Ti/Pt/Au for brazing), and surface finishes (Ra < 1nm) required for these demanding RF and optical submount applications.
Technical Specifications
Section titled āTechnical Specificationsā| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Thermal Conductivity (TC) | 1500 | W/(mĀ·K) | Ultimate thermal spreader material |
| Diamond CTE | 1.4 | ppm/K | Ideal match for high-power semiconductors |
| GaN CTE | 3.2 | ppm/K | Semiconductor requiring thermal matching |
| Required TC Range (Flange) | 140 to 1000 | W/(mĀ·K) | Range demanded by high-power applications |
| Required CTE Range (Flange) | 2.3 to 24 | ppm/K | Range for reliable bonding |
| Minimum RF Lead Width | 0.35 | mm | Required for optimized RF/microwave impedance |
| Minimum Shear Strength (Post-Bonding) | > 100 | KgF | Required mechanical integrity after brazing |
| Cavity Volume (Miniature RF Package) | 2.78 | mm3 | Example of miniature package vulnerability to outgassing |
| Gold Trace Width | > 2.5 | Āµm | Required for high current pathways on insulators |
| Insulator Dielectric Constant (Al2O3) | 9.8 | 1MHz | Used for high-power electrical circuits |
Key Methodologies
Section titled āKey MethodologiesāThe GenPackā¢ RF and Photonic packaging methodology relies on precise material selection and advanced bonding techniques to ensure high thermal and electrical performance:
- Material Selection: Insulators (e.g., Alumina Oxide, Silicon Nitride) and flanges (Diamond, CuW, CuMoCu) are selected based on high TC and CTE matching requirements relative to the semiconductor (GaN, GaAs).
- Organic-Free Brazing: Insulators are bonded to the thermal spreader/flange using high-melting-temperature braze materials (e.g., Gold-Tin, Tin-based, or Indium-based alloys) to eliminate performance degradation caused by organic outgassing.
- Circuit Integration: Custom electrical traces (Gold lines > 2.5 Āµm wide) are deposited onto the ceramic insulators to create low-resistance, high-current pathways.
- Vias and Grounding: Multiple thru-holes (vias) are formed in the ceramic substrates and filled with metal braze alloy. These vias provide a low DC resistance path, reduce high-frequency electrical impedance, and significantly increase the mechanical bonding strength (> 100 KgF).
- Lead Fabrication: RF leads are fabricated and bonded using high-melting braze, with widths tapered down to 0.35 mm to optimize signal impedance at RF and microwave frequencies.
- Reliability Testing: Completed packages are subjected to rigorous 1000-cycle Temperature Cycle Testing (TCT) to validate long-term mechanical stability and thermal performance.
6CCVD Solutions & Capabilities
Section titled ā6CCVD Solutions & CapabilitiesāThe research highlights that diamond is the optimal material for high-power thermal spreaders and submounts. 6CCVD is uniquely positioned to supply the custom MPCVD diamond required to replicate and advance this GenPackā¢ technology for RF and Photonic applications.
Applicable Materials
Section titled āApplicable MaterialsāTo achieve the 1500 W/(mĀ·K) TC and 1.4 ppm/K CTE cited in the paper, 6CCVD recommends the following materials:
| 6CCVD Material | Description | Application Fit | Key Benefit |
|---|---|---|---|
| Optical Grade SCD | High-purity Single Crystal Diamond (SCD). | High-power GaN/GaAs submounts, laser diode heat sinks, critical photonics. | Maximum Thermal Conductivity (up to 2000 W/(mĀ·K)) and lowest RF loss. |
| High-Purity PCD | Polycrystalline Diamond (PCD) with controlled grain size. | Large-area RF flanges (up to 125mm), high-power spreaders. | Excellent TC (up to 1500 W/(mĀ·K)) at larger, scalable dimensions. |
| Boron-Doped Diamond (BDD) | SCD or PCD doped with Boron. | Integrated thermal spreader and low-resistance electrode/ground plane. | Combines high TC with tunable electrical conductivity (p-type semiconductor). |
Customization Potential
Section titled āCustomization Potentialā6CCVDās in-house capabilities directly address the complex fabrication and assembly requirements of the GenPackā¢ architecture:
- Custom Dimensions: We supply diamond plates and wafers up to 125mm in diameter (PCD) and custom shapes, suitable for flange and thermal spreader applications far exceeding typical lab sizes.
- Precision Thickness Control: SCD and PCD layers can be grown from 0.1 Āµm up to 500 Āµm for optimal thermal path design, or supplied as substrates up to 10mm thick for robust flanges.
- Advanced Metalization: The organic-free brazing process requires specific metal stacks (e.g., Ti/Pt/Au, Ti/W/Au) for reliable bonding to the diamond surface. 6CCVD offers internal, custom metalization services (Au, Pt, Pd, Ti, W, Cu) tailored for high-temperature braze alloys.
- Surface Finish: For optimal thermal contact and low-loss RF performance, 6CCVD guarantees ultra-smooth polishing: Ra < 1nm for SCD and Ra < 5nm for inch-size PCD.
Engineering Support
Section titled āEngineering Supportā6CCVDās in-house PhD team specializes in material science and thermal modeling for high-power semiconductor integration. We provide comprehensive support for:
- CTE Matching Optimization: Assisting engineers in selecting the precise diamond grade and metalization stack to ensure maximum shear strength and reliability between GaN/GaAs devices and the diamond submount.
- RF Loss Minimization: Consulting on surface finish and material purity to minimize dielectric loss tangent (tan Ī“) for high-frequency (5G and beyond) RF and microwave applications.
- Custom Via and Circuit Design: Collaborating on the integration of metal-filled vias and custom circuit patterns onto diamond or ceramic insulators for optimized thermal and electrical pathways.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
RF signals are radio waves that are very crucial for telecommunications. Quality communications require reliable materials which are appropriately processed to house high-powered semiconductors such as GaN and GaAs. It is equally crucial to accommodate passive electronic components along with these semiconductors into the housings for the Next Generation RF package or GenPackā¢. Evolving semiconductor technologies demand fail-safe packages to protect the devices in all applications and environmental conditions. Future aircraft, EV cars, spacecraft, augmented and/ or virtual reality headsets, medical devices and many more technologies require operating at a higher power and frequency with a proper thermal and power management platform. The higher speeds of telecommunications hinge on the performance of semiconductors and their packages. Therefore, the GenPackā¢ and packaging process are becoming crucial pieces of the supply chain. Rugged GenPackā¢ RF packages differ in several ways compared to the traditional air cavity packages. For instance, FR-4 or Flame-Retardant glass-reinforced epoxy laminate material can be replaced with Aluminum Nitride or Alumina Oxide, Silicon Nitride or even Sapphire. The switch offers mechanical bonding directly onto the thermal spreader. Traditional circuits created on printed circuit boards have limited ability to dissipate heat due to the low thermal conductivity of FR4. Circuits created on ceramic can dissipate higher amounts of heat. As in the organic FR4 boards, multiple vias can be formed in the ceramic substrates to create metal pads top the ceramic that are grounded to the flange beneath the ceramic. A metal flange can be positioned beneath the ceramic to provide a heat spreader and electrical ground that can be bolted onto a heatsink. Flanges can be made from a diamond metal matrix composite instead of lower thermal conductivity materials to provide much more efficient thermal transfer. Furthermore, narrow leads offer optimized impedance at RF and microwave frequencies. A range of ceramic and flange materials can be selected to optimize GenPackā¢ RF Packages with cost, quality, and performance in considerations for the respective applications.