Applications of Multilayer PCBs in Aerospace Electronic Equipment

　　Multilayer PCBs are indispensable in aerospace applications, where extreme environmental conditions (temperature, vibration, radiation) and strict performance requirements demand robust, high-reliability solutions. Their use spans avionics, satellite systems, propulsion controls, and more.

　　1. Avionics and Flight Control Systems

　　High-Layer-Count Boards (30–100 Layers):

　　Used in flight control computers (FCCs) and inertial navigation systems (INS). For example, a 60-layer board in a military aircraft’s FCC integrates analog signal processing, digital control, and power management layers, with embedded resistors/capacitors for compactness.

　　Features: Tight impedance control (50 Ω ±5%) for 1 GHz+ signals, radiation-hardened materials (e.g., Rogers RO4835 with α-particle suppression), and hermetic sealing to prevent moisture ingress.

　　Ruggedization:

　　Conformal coating (e.g., Parylene C) protects against salt fog and chemical spills.

　　Vibration damping via underfill beneath BGAs and flex-rigid constructions for moving parts (e.g., retractable antennas).

　　2. Satellite and Spacecraft Electronics

　　Thermal Cycling Resistance:

　　Multilayer boards in satellite payloads must withstand -180°C to +125°C temperature swings. Materials like polyimide (CTE=15 ppm/°C) with aluminum cores reduce stress from CTE mismatch between silicon chips (CTE=3 ppm/°C) and PCB.

　　Phase-change materials (PCMs) embedded between layers absorb heat during solar exposure and release it in shadowed orbits.

　　Radiation Hardening:

　　Use of quartz-based dielectrics (Dk=3.7, radiation tolerance>10⁶ rads) and gold-plated copper in high-altitude or deep-space missions.

　　Cross-strapping vias (redundant vias per net) ensure signal integrity if some vias fail due to radiation-induced degradation.

　　3. Propulsion and Engine Control Units (ECUs)

　　High-Temperature Performance:

　　Boards near jet engines or rocket thrusters use ceramic-filled laminates (e.g., Arlon AD325, Tg=325°C) and silver-plated copper (melting point=961°C) for power layers. A 16-layer board in a turbofan ECU operates at 250°C continuously, with thermal vias connecting to a heat sink.

　　High-Power Handling:

　　Thick copper layers (3–5 oz) and embedded inductors manage 100+ Amps for motor drives. Isolated power planes (≥200 V isolation) prevent arcing in high-voltage systems (e.g., electric aircraft).

　　4. Radar and Microwave Systems

　　RF/Microwave Integration:

　　Multilayer RF boards (e.g., Rogers RT/duroid 5880) with embedded antennas and passive components (e.g., couplers, filters). A 12-layer phased-array radar board uses 50 μm microstrip lines and buried cavities for MMICs, achieving <0.5 dB insertion loss at 24 GHz.

　　Antenna-in-Package (AiP) Designs:

　　Sequentially laminated layers integrate patch antennas, phase shifters, and low-noise amplifiers (LNAs) in a single board, reducing interconnection losses. Used in satellite communications (Ka-band) and airborne radar systems.

　　5. Reliability and Certification

　　Qualification Standards:

　　Compliant with IPC-6012 Class 3A (high-reliability aerospace) and AS9100 for quality management.

　　Burn-in testing (1,000 hours at 125°C) and X-ray inspection for via integrity.

　　Redundancy Design:

　　Dual-rail power distribution and parallel signal paths (e.g., primary/backup flight control signals on separate layers) ensure fail-safe operation.

　　Case Study: The Mars Rover’s electronics use 30-layer ceramic-core PCBs with gold-plated vias, capable of withstanding 85 kRad radiation and -140°C cold starts. These boards integrate radiation-hardened FPGAs, sensor interfaces, and thermal control circuits, demonstrating the critical role of multilayer PCBs in extreme aerospace environments.

　　As aerospace systems evolve toward higher integration (e.g., more electric aircraft,