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 |
Executive Summary
Section titled āExecutive SummaryāThe GenPackā¢ platform introduces rugged, organic-free packaging solutions designed for Next Generation high-power RF, microwave, and optical devices, focusing on superior thermal and electrical performance.
- Thermal Management: Achieves high thermal dissipation by replacing traditional low-conductivity FR-4 materials (0.2 W/(m-K)) with advanced ceramics (e.g., AlN at 200 W/(m-K)) and high-performance flanges (up to 1500 W/(m-K) for Diamond).
- Organic-Free Assembly: Utilizes high-melting-temperature braze alloys for all component attachments (insulator-to-flange, leads-to-circuit), eliminating outgassing issues associated with epoxy die attach, which is critical for high-reliability and optical applications.
- Mechanical Robustness: Demonstrated exceptional mechanical integrity, maintaining a bonding shear strength of greater than 100 KgF even after 1000-cycle temperature testing.
- CTE Matching: Flange and insulator materials are carefully selected to match the Coefficient of Thermal Expansion (CTE) of high-power semiconductors (like GaN, CTE 3.2 ppm/K) across a required range of 2.3 ppm/K to 24 ppm/K.
- RF Optimization: Features narrow RF leads (down to 0.35 mm width) and metal-filled vias in the ceramic substrate to optimize signal impedance, reduce DC resistance, and support high current pathways.
- Versatile Insulators: Offers a selection of ceramic insulators (Al2O3, AlN, Si3N4) with tailored dielectric constants (7.8 to 9.8 at 1 MHz) to meet specific RF performance requirements.
Technical Specifications
Section titled āTechnical Specificationsā| Parameter | Value | Unit | Context |
|---|---|---|---|
| Max Flange Thermal Conductivity (Diamond) | 1500 | W/(m-K) | Highest TC material option |
| Typical Insulator Thermal Conductivity (AlN) | 200 | W/(m-K) | Aluminum Nitride ceramic |
| Traditional Material Thermal Conductivity (FR-4) | 0.2 | W/(m-K) | Flame-Retardant laminate baseline |
| Required CTE Range (Package Materials) | 2.3 to 24 | ppm/K | Range for optimal thermal expansion matching |
| GaN Semiconductor CTE | 3.2 | ppm/K | Gallium Nitride reference |
| Alumina Oxide (Al2O3) CTE | 7 | ppm/K | Common ceramic insulator reference |
| Minimum RF Lead Width | 0.35 | mm | Optimized for signal impedance |
| Bonding Shear Strength (Post-Test) | >100 | KgF | Maintained after 1000 temperature cycles |
| Dielectric Constant (Al2O3) | 9.8 | 1 MHz | Insulator material property |
| Dielectric Constant (Si3N4) | 7.8 | 1 MHz | Insulator material property |
| Minimum Gold Line Width (Circuits) | >2.5 | Āµm | For high current pathways |
| Example Optical Cavity Volume | 2.78 | mm3 | Miniature package size vulnerable to outgassing |
Key Methodologies
Section titled āKey MethodologiesāThe GenPackā¢ assembly process focuses on organic-free, high-temperature bonding of CTE-matched materials:
- Flange Material Selection: A thermal spreader (flange) is chosen from materials like Cu-CuMo-Cu, Copper Tungsten (CuW), or Diamond metal matrix composites (Ag-Diamond, Cu-Diamond) to meet specific thermal conductivity and CTE requirements.
- Insulator Preparation: Ceramic insulators (e.g., Alumina Oxide, Silicon Nitride, Aluminum Nitride) are prepared with a plurality of thru-holes (vias) configured in a pattern along the electrical circuits.
- Insulator-Flange Bonding: The insulator is bonded directly to the flange using organic-free, high-melting-temperature braze materials, ensuring high shear strength and thermal transfer.
- Circuit Deposition: Organic-free electrical circuit traces (gold lines >2.5 Āµm wide) are deposited onto the top surface of the ceramic insulator.
- Via Filling: Vias within the ceramic insulator are filled with bonding braze alloy to create low DC resistance paths for high current and enhance mechanical bonding strength in parallel.
- Lead Attachment: Narrow RF leads (fabricated to taper down to 0.35 mm width) are attached to the electrical circuits using organic-free, high-melting-temperature braze alloy.
- Quality Verification: Packages are subjected to rigorous testing, including post-bonding shear tests and 1000-cycle temperature tests, to confirm bonding strength and reliability.
Commercial Applications
Section titled āCommercial ApplicationsāThe GenPackā¢ packaging technology is designed to support high-reliability, high-power density devices across several critical industries:
- Telecommunications: 5G and beyond infrastructure, high-speed digital and radio frequency applications requiring high signal integrity and power output.
- High Power RF/Microwave: Housing for high-powered semiconductors such as GaN FETs, GaAs MMICs, and Si LDMOS transistors.
- Aerospace and Defense: Future aircraft, spacecraft, and high-reliability defense electronics requiring fail-safe operation under extreme conditions.
- Automotive: Electric Vehicle (EV) power electronics and high-speed communication systems.
- Consumer Electronics: Augmented Reality (AR) and Virtual Reality (VR) headsets requiring miniature, high-performance packages.
- Medical Devices: Applications demanding reliable, high-power operation.
- Photonics and LED Management: Optical packages and System in Package (SIP) solutions for light-emitting and receiving semiconductors, leveraging thermal spreaders and optical windows with anti-reflective/bandpass coatings.
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.