Innovative Multi-Domain Optimization in Extreme Environment Electronics

Crane Aerospace & Electronics has developed a groundbreaking multi-domain integration approach, Multi-Mix® Technology, which optimizes electromagnetic performance, thermal management, and long-term reliability. This method ensures superior performance in mission-critical aerospace and defense applications.

This technical analysis examines abreakthrough integration methodology developed by Crane Aerospace & Electronics that fundamentally reimagines how complex electronic systemsare designed for mission-critical applications. Crane Aerospace &Electronics employs an integrated, multi-domain design approach thatholistically optimizes electromagnetic performance, thermal management, and long-term reliability. This ensures their solutions meet the stringent demands of aerospace and defense applications.

Fundamental Challenges in Modern RFCircuit Integration

The design and fabrication of radio frequency(RF) circuits for aerospace and defense applications presents a confluence of exceptionally demanding engineering challenges.

The sesystems must simultaneously optimize across multiple physical domains while operating reliably in extreme environments, creating complex multi-variable design problems that traditional approaches struggle to resolve.

‍1.     Electromagnetic Field Propagation Complexities

The physics of high-frequencyelectromagnetic propagation creates fundamental challenges that intensify as frequencies increase into the millimeter-wave spectrum. In traditional multilayer circuit constructions, these manifest as:

a.    Impedance Discontinuities at Material Interfaces

Each material transition in a conventional multilayer stack-up creates an impedance discontinuity due to the different dielectric constants and structures of the substrate and bonding materials. At Ka-band frequencies and above, even minor discontinuities produce significant effects:

• Return loss degradation of 3-5 dB per interface
• Group delay variations exceeding 0.2 ns across operating bands
• Standing wave patterns that create frequency-dependent response ripple (±1.5 dB)
• Phase non-linearities that distort signal modulation

Conventional solutions using sequential quarter-wave matching sections consume precious board area and only work effectively over narrow frequency bands, making wideband operation particularly problematic.

b.    Mode Conversion at Transitions and Bends

As signals navigate through complex circuit topologies, traditional designs face unwanted mode conversions:

• Quasi-TEM to surface wave conversion at bends and transitions, causing:
   
  • Unpredictable radiation losses (0.1-0.3 dB/transition at Ka-band)
   
  • Interference between adjacent signal paths
   
  • Resonant coupling effects at specific frequencies

Modern electronic warfare (EW) systems face significant challenges in RF performance while adhering to stringent size, weight, and power (SWaP) constraints. Conventional design methodologies that treat electromagnetic, thermal, and mechanical aspects separately often lead to performance trade-offs.

Mode conversion is particularly problematic in beamforming networks where differential phase errors directly impact beam pointing accuracy. A phase error of just 5° at 30 GHz can result in beam pointing errors exceeding 1° in a phased array system.

c.    Surface Roughness Effects at Higher Frequencies

The conductor surface profile becomes increasingly significant at millimeter-wave frequencies due to skin effect phenomena:

• Surface roughness-induced losses increase approximately as the square root of frequency
• At Ka-band, roughness contributes additional losses of 0.35 dB/GHz/cm
• Conventional copper foils with RMS roughness of 2-3 μm create significant uncontrolled loss variations

2.     Thermal ManagementBarriers in High-Density Designs

Traditional RF circuit constructions createmajor thermal management challenges that directly impact performance:

a.    Thermal Conductivity Mismatches

Conventional multilayer constructionscontain materials with widely varying thermal conductivities:

• PTFE-based substrates: 0.20-0.30 W/m·K
• Prepreg bonding films: 0.15-0.25 W/m·K
• Copper conductors: ~400 W/m·K

These mismatches create severe thermal bottlenecks at material interfaces. In a typical 8-layer construction withmixed materials, the effective through-plane thermal conductivity is oftenlimited to less than 0.2 W/m·K, despite having copper layers that couldtheoretically conduct heat more efficiently.

b.    Critical ThermalGradient Effects on RF Performance

The thermal gradients resulting frominadequate thermal management directly impact circuit performance throughmultiple mechanisms:

• Oscillator frequency drift: Typically 100-500 kHz/°C for VCOs operating at X-band
• Amplifier gain variation: 0.05-0.10 dB/°C for GaAs MMICs
• Phase shifter accuracy: 1-2°/°C for typical phase control elements
• Filter center frequency drift: 20-50 ppm/°C for microstrip filters

These temperature-dependent variationscreate significant design margins that must be allocated, directly reducingusable performance. In wideband electronic warfare receivers, thermalmanagement inadequacies can reduce the effective spurious-free dynamic range by3-8 dB.

c.    Thermal Cycling InducedFailures

The mismatch in coefficient of thermalexpansion (CTE) between different materials creates mechanical stress duringthermal cycling:

• PTFE-based substrates: 70-280 ppm/°C (highly anisotropic)
• Prepreg bonding films: 40-80 ppm/°C
• Copper conductors: 17 ppm/°C
• Ceramic components: 6-10 ppm/°C

These CTE mismatches result in:

• Solder joint fatigue (typical MTBF reduction of 40-60% in     severe environments)
• Via barrel cracking after 500-1000 thermal cycles
• Delamination at material interfaces
• Micro-cracking in components due to induced strain

3.     Size, Weight, and Power(SWaP) Constraints

Aerospace and defense platforms imposeincreasingly stringent SWaP requirements that conventional RF circuittechnologies struggle to meet:

Conflicting Requirements for ComplexSystems

Modern electronic warfare, radar, andcommunication systems require:

• Wider frequency coverage (often DC to 40+ GHz)
• Higher channel counts for multi-function operation
• Increased processing capacity
• All within smaller allocations of size, weight, and power

Conventional approaches to addressing theserequirements typically involve:

• Physically separated functional blocks with interconnects
• Additional isolation structures to minimize interference
• Separate thermal management systems
• Complex mechanical packaging

This approach creates inherently inefficient solutions with significant overhead in terms of size and weight dedicated to interconnection, isolation, thermal management, and mechanical support rather than core functionality.

Limitations of Traditional Manufacturing Approaches

Sequential Design Methodology Pitfalls

The conventional approach to RF circuit design treats electromagnetic, thermal, and mechanical considerations as separate, sequential design tasks. This creates a cascading series ofcompromises:

1. Electromagnetic optimization comes first, focusing on electrical performance
2. Thermal management is added as a secondary consideration, often     compromising the electromagnetic design
3. Mechanical packaging is the final constraint, further     compromising both electromagnetic and thermal performance

This sequential approach inevitably leadsto suboptimal designs, as each stage constrains the next with inadequateconsideration of the coupled nature of these physical domains.

Manufacturing Process Limitations

Traditional PCB manufacturing processesface fundamental limitations that impact performance:

a.    Registration AccuracyChallenges

Conventional multilayer PCB processestypically achieve layer-to-layer registration accuracies of ±50 μm at best.This presents significant challenges for:

• Phase-matched transmission lines where 50 μm corresponds to approximately 5° of phase at 30 GHz
• Via placement precision for complex 3D routing
• Component land pattern alignment

b.    Via Technology Constraints

Traditional PCB processes face several via-related limitations:

• Aspect ratio limitations (typically 10:1 maximum)
• Requirements for through-hole vias that consume space on all layers
• Sequential build-up processes with limited layer counts
• Back-drilling requirements that add cost and reduce reliability

These limitations directly impact theability to implement complex 3D routing architectures needed for optimal RFperformance in dense systems.

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Crane's Multi-Mix®Technology: A Fundamental Paradigm Shift

Rather than making incremental improvementsto conventional approaches, Crane Aerospace & Electronics' Multi-Mix®technology represents a fundamental reimagining of RF circuit integrationthrough a unified approach to electromagnetic, thermal, and mechanical design.

o   Material Science Foundation: Fusion Bonding

At the core of Multi-Mix® technology is aproprietary autoclave fusion bonding process that creates a true three-dimensional homogeneous circuit architecture:

Elimination of Bonding Films

Unlike conventional multilayer circuitsthat rely on prepreg bonding films to attach substrate layers, Multi-Mix®employs direct fusion of PTFE (Teflon®) layers under precisely controlled conditions of temperature, pressure, and time. This creates a homogeneous structure with no material interfaces, resulting in:

• Complete elimination of impedance discontinuities at layer boundaries
• Near-zero interfacial thermal resistance between layers
• Uniform mechanical properties throughout the structure
• Measured insertion loss reduction of 0.5 dB/inch compared to conventional constructions

Precise Crystalline Structure Control

The fusion bonding process precisely controls the crystall ine structure of the PTFE material, creating:

• Uniform dielectric properties throughout the structure
• Consistent thermal expansion characteristics
• Enhanced mechanical strength at interlayer boundaries
• Imperviousness to delamination even under extreme thermal cycling

Heterogeneous Material System Integration

Multi-Mix® employs a strategic approach tomaterials selection, integrating diverse materials optimized for specificfunctions:

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RF Performance Materials

• PTFE-based substrates (such as Rogers RO3000 and RO6000) with very low loss (loss tangent < 0.002 @ 10 GHz)
• High-permittivity ceramics for circuit miniaturization
• Enhanced metallization to reduce skin effect losses

o   Thermal Management Integration

The homogeneous structure of Multi-Mix®technology enables superior thermal management through:

• Direct thermal pathways from heat-generating components to heat sinks
• Elimination of thermal barriers at layer interfaces
• Metal-matrix composites combining strength with thermal conductivity
• Controlled-CTE materials to minimize thermal stress

This integrated thermal approach resultsin:

• Measured temperature gradients less than 3°C across assemblies (compared to >10°C in conventional designs)
• Peak temperatures reduced by 12°C without additional cooling structures
• Consistent RF performance across wide operating temperature ranges

True Three-Dimensional Architecture

The Multi-Mix® technology enables avolumetric approach to circuit design that fundamentally changes how complex RFsystems are implemented:

Unlimited Via Architecture

The fusion bonding process allows for:

• Unlimited blind and buried vias without the need to backdrill or backfill
• Via aspect ratios exceeding 50:1
• Laser-drilled precision vias with positional accuracy better than ±25 μm
• Strategic via placement for optimal signal routing, thermal management, and mechanical integrity

Three-Dimensional Routing Capabilities

This advanced via architecture enables:

• Optimal signal routing in all three dimensions
• Precise phase matching between RF channels (±2° at Ka-band in production units)
• Strategic placement of ground planes and shields within the structure
• Channel-to-channel isolation improvement of >15 dB compared to traditional approaches

Embedded Functional Structures

The volumetric architecture allows for:

• Embedded cavities forming waveguide structures
• Integrated resonators with Q-factors exceeding 500 at Ka-band
• Precision thin-film resistors with tolerances of ±0.1%
• Embedded thermal management pathways

‍Technical Performance Validation

The benefits of Multi-Mix® technology have been quantitatively validated across multiple performance dimensions:

Physical Form Factor Optimization

Compared to conventional implementations ofequivalent functionality:

• 40% volume reduction (from 2.3L to 1.4L in a representative EW receiver)
• 30% weight reduction (from 1.2kg to 0.84kg)
• Simplified external interfaces

Thermal Management Performance

• 12°C lower maximum component temperature
• Temperature gradients reduced to less than 3°C (compared to >10°C in conventional designs)
• Elimination of additional cooling structures in many     applications

RF Performance Enhancement

• Receiver Sensitivity: Improved by 3 dB through reduced losses
• Phase Noise: Decreased by 7 dB at 10 kHz offset due to improved     thermal stability
• Spurious Emissions: Reduced by 22 dB through better isolation
• Channel Isolation: >15 dB improvement through optimized 3D architecture

Reliability Enhancement

• MTBF increased from 15,000 hours to 34,500 hours (130% improvement)
• Field-proven with over 2.6 million operating hours with zero failures
• Demonstrated survival in extreme environments (temperature cycling, vibration, shock)

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‍Case Study: Ka-Band Beamforming Network

A 26-layer Ka-band beamforming network demonstrates the capabilities of Multi-Mix® technology in addressing complex RFintegration challenges:

Technical Requirements

• 16 phase-matched channels with ±3° matching at 30 GHz
• Operation from -55°C to +125°C with consistent performance
• 40% size reduction from previous generation
• Enhanced reliability in high-vibration environments

Implementation Challenges

• Complex signal routing requiring over 500,000 blind vias
• Critical thermal management at multiple amplifier locations
• Stringent phase and amplitude matching across temperature
• High channel density with demanding isolation requirements

Multi-Mix® Solution

• Fully integrated 26-layer structure with direct fusion bonding
• Strategic placement of thermal pathways beneath amplifiers
• 3D routing architecture maintaining precise electrical path lengths
• Embedded shielding structures for channel isolation

Measured Results

• Phase matching of ±2.1° across temperature range (exceeding requirement)
• Peak temperatures reduced by 14°C compared to conventional design
• Channel isolation increased by 18 dB
• 43% size reduction achieved
• MTBF improved from 22,000 to 51,000 hours

Specialized Substrate Materials

Complementing Multi-Mix® technology, Craneoffers specialized substrate materials that provide unique advantages for specificapplications:

a.    CuFlon® Technology

CuFlon® is a unique microwave substratematerial consisting of copper conductors plated directly onto virgin PTFE(Teflon®) dielectric substrate without any adhesives or binders. Thisconstruction offers exceptional performance characteristics:

• Ultra-low loss (loss tangent ~0.0003 from DC to Ku Band)
• Stable dielectric constant over wide temperature and frequency ranges
• High operating temperature (up to 200°C continuously)
• Perfect isotropy (anisotropy ratio of 1.0 compared to 1.02-1.20 for PTFE/glass)
• Negligible moisture absorption (<0.01%)

These properties make CuFlon® particularlyvaluable for applications requiring minimal signal loss:

• Narrow-bandwidth band pass filters
• Long transmission line applications (phase shifters, delay lines)
• Super low-loss components in high power or low-noise applications

Measurements have shown that CuFlon® canprovide 2-2.5 dB power output improvement over similar circuits built onTeflon-glass substrates. The doubler loss in one X-band VCO example was only3.9 dB, which approaches the theoretical optimum of 3.0 dB.

b.    NorCLAD™ Laminates

NorCLAD™ is manufactured from a modifiedversion of the thermoplastic PPO (Polyphenylene Oxide) and offers:

• Dielectric constant of 2.55 with high uniformity
• Low dissipation factor of 0.0011 at 3 GHz
• Uniform and reproducible electrical properties
• High stability over temperature (-55°C to 125°C)
• Resistance to aqueous processing chemicals

These properties make NorCLAD™ ideal for RFand microwave applications at a price point below materials offering comparableperformance. Typical applications include GPS systems, UAVs, SatComsubscribers, and broadband communication links.

Manufacturing Implementation

The successful implementation of Multi-Mix®technology requires specialized manufacturing processes:

Advanced Material Preparation

• Precision ceramic grinding to thicknesses of 75μm with ±5μm tolerance
• Specialized metallization techniques minimizing stress at material interfaces
• Custom material formulations for optimal electromagnetic, thermal, and mechanical properties

Precision Fabrication Processes

• Laser micro-via formation with positional accuracy better than ±15μm
• Multi-step autoclave fusion bonding under precise time/temperature/pressure profiles
• Advanced metallization with >50:1 aspect ratio capability

Comprehensive Test and Validation

• In-process RF testing at critical fabrication stages
• Non-destructive evaluation using microwave-frequency CT scanning
• Comprehensive environmental stress screening including thermal shock, vibration, and humidity

Conclusion

Crane Aerospace & Electronics'Multi-Mix® technology represents a fundamental advance in RF circuitintegration for aerospace and defense applications. By simultaneously addressing electromagnetic, thermal, and mechanical challenges through aunified 3D architecture, Multi-Mix® delivers performance improvements that would be unachievable through conventional approaches.

The measured improvements in physical formfactor (40% volume and 30% weight reduction), thermal performance (12°C lower temperatures), RF performance (enhanced sensitivity, reduced phase noise,improved isolation), and reliability (130% MTBF improvement) validate the effectiveness of this integrated approach to RF circuit design.

For mission-critical aerospace and defense applications where performance, reliability, and SWaP optimization are paramount, Multi-Mix® technology provides a solution that breaks through the limitations of conventional RF circuit construction methods.

‍SAGA Components AB: Your Trusted Partnerfor Crane's Advanced Microwave Technologies in the Nordics

Delivering Cutting-Edge Aerospace & Defense Electronics

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Technical Solutions Manager: Morteza Ebadi, PhD.  

• Email: morteza.ebadi@sagacomponents.com

• Direct: +46 (0) 72 300 7287

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