Chapter 1 Thermal management performance
I. Technical indicators of ceramic shells
1. High thermal conductivity and thermal diffusion performance
The thermal conductivity of ceramic shells (such as alumina and aluminum nitride 170-230 W/(m·K)) is significantly higher than that of plastic and metal packaging materials, which can quickly transfer the heat generated by the chip to the external environment to avoid local overheating. Aluminum nitride is suitable for high-power sensor packaging. Its excellent thermal diffusion performance can evenly distribute heat and reduce the impact of thermal stress on the sensor.
2. Low coefficient of thermal expansion (CTE)
The thermal expansion coefficient of ceramic materials is close to that of silicon chips (such as Al₂O₃’s CTE is about 6-8 ppm/℃), which can effectively reduce thermal stress caused by temperature changes, avoid cracking of the packaging interface or chip damage, and improve the long-term stability of the sensor.
3. Combination of airtightness and thermal stability
The ceramic shell adopts airtight packaging technology (such as HTCC process), which can not only isolate external environmental interference such as moisture and dust, but also maintain the stability of thermal management performance under harsh conditions such as high temperature and high humidity. CPGA (ceramic pin grid array) packaging shows excellent high temperature resistance and reliability in high-frequency and high-power sensors.
4. Structural optimization enhances heat dissipation path
The new ceramic shell further improves the heat dissipation efficiency through design innovation. By setting a heat sink block and mounting groove at the bottom of the CPGA shell, the internal heat is directly directed to the external heat dissipation structure, significantly reducing the chip operating temperature, which is suitable for highly integrated sensors.
2. Technical indicators of ceramic substrates (substrates)
1. High thermal conductivity and thermal stability
Ceramic substrates (such as Al₂O₃, AlN substrates) have high thermal conductivity (AlN can reach 150-200 W/(m·K)), which can quickly export the heat generated by MEMS sensors and maintain the stability of chip operating temperature. At the same time, its high temperature resistance (operating temperature can reach above 1000℃) is suitable for high temperature environment applications.
2. Thermal expansion coefficient matching and mechanical strength
The thermal expansion coefficient of the ceramic substrate is highly matched with the silicon-based chip, reducing the interface stress during the thermal cycle and avoiding the generation of microcracks. The CTE difference between the alumina substrate and the silicon chip is less than 1 ppm/℃, which significantly improves the packaging reliability. The high mechanical strength of ceramics (such as Al₂O₃ bending strength ≥300 MPa) can protect the sensor from mechanical shock.
3. Three-dimensional structure and thermal management integration
The ceramic substrate supports micromachining technology, and can design complex three-dimensional structures (such as microchannels, cavities) to optimize the heat dissipation path. Silicon nitride ceramic substrates combine multi-layer wiring with cavity design to meet the needs of MEMS movable structures and achieve efficient heat dissipation.
4. Chemical stability and insulation
The corrosion resistance and high insulation (dielectric strength > 10 kV/mm) of ceramic materials enable them to maintain thermal management performance in humid and corrosive environments, avoiding the risk of thermal runaway caused by leakage or short circuit.
III. Comprehensive application scenarios and trends
• High-power sensors: In industrial lasers and microwave devices, ceramic shells achieve efficient heat dissipation through HTCC process and heat sink structure.
• MEMS sensors: Ceramic substrates use vacuum air sealing and thermal expansion matching technology to ensure the stable operation of micromechanical structures.
• Emerging fields: In scenarios such as 5G communications and AI computing, highly integrated ceramic packages (such as CBGA and CQFN) are combined with intelligent thermal design algorithms to further optimize thermal management efficiency.
Chapter 2 Electrical performance
1. Low dielectric constant and high-frequency performance
Ceramic materials (aluminum oxide, aluminum nitride) have low dielectric constants (the dielectric constant of aluminum nitride is only 1/3 of that of aluminum oxide), which can reduce energy loss in high-frequency signal transmission and are suitable for RF sensors and microwave devices.
2. High insulation and electrical strength
Alumina ceramics have high insulation resistance (>10¹² Ω·cm) and a breakdown voltage of 15-25 kV/mm, which can effectively isolate the internal circuit of the sensor from the external environment and prevent leakage and breakdown risks.
3. Excellent thermal conductivity and thermal stability
The thermal conductivity of aluminum nitride (AlN) is as high as 170-230 W/(m·K), which is more than 4 times that of aluminum oxide. It can quickly remove the heat generated by the sensor chip and avoid performance drift caused by temperature rise. Its thermal expansion coefficient is close to that of silicon chips (AlN is 4.5×10⁻⁶/℃), reducing thermal stress damage.
4. Low dielectric loss and signal fidelity
The loss tangent (tan δ) of ceramic materials is as low as 0.0002-0.002 (@1MHz), which can significantly reduce signal distortion and improve measurement accuracy in high-frequency sensors.
5. Airtightness and chemical stability
The ceramic package shell achieves airtight sealing (leakage rate <1×10⁻⁸ Pa·m³/s) through the HTCC process, which can block moisture and corrosive gases from corroding the sensor’s sensitive components and extend its service life.
6. Temperature coefficient matching and stability
The temperature coefficient of resistance (TCR) of the ceramic material (Al₂O₃) is controllable, and the PTC/NTC characteristics can be customized (the barium titanate PTC resistance mutation temperature reaches 120-300℃), which is suitable for precise temperature control of temperature sensors.
7. Anti-electromagnetic interference capability
The shielding effectiveness of the ceramic substrate can reach 60-80 dB (@1GHz), which effectively suppresses external electromagnetic interference and ensures the integrity of the sensor signal, especially in automotive electronics and industrial automation scenarios.
Typical application cases include:
MEMS sensor: Silicon nitride (Si₃N₄) substrates are used for vibration-resistant packaging of inertial sensors due to their high mechanical strength (>800 MPa) and low thermal expansion coefficient.
High-temperature sensor: Zirconium oxide (ZrO₂) substrates maintain stable dielectric properties above 600°C and are suitable for engine combustion monitoring.
Humidity sensor: Alumina ceramic substrates achieve high-precision capacitive humidity detection through surface metallization, and the dielectric constant temperature drift is <0.1%/°C.
In summary, ceramic materials have achieved a synergistic improvement in electrical, thermal and mechanical properties in the sensor field by optimizing components (Al₂O₃/AlN composite) and processes (DPC metallization).
Chapter 3 Mechanical Strength and Reliability
1. High Compressive and Flexural Strength
The compressive strength of alumina (Al₂O₃) ceramics can reach 2,500MPa and the flexural strength can reach 300MPa. Aluminum nitride (AlN) achieves higher toughness through whisker reinforcement and can withstand the mechanical stress of sensors in vibration or impact environments.
2. Low thermal expansion coefficient matching
The ceramic material (AlN thermal expansion coefficient 4.5×10-6/℃) is close to that of silicon chips (3×10-6/℃), reducing the risk of interface delamination caused by thermal cycles and is suitable for industrial sensors with large temperature fluctuations.
3. High elastic modulus and rigidity
The elastic modulus of alumina is 380GPa, and the mechanical strength of silicon nitride (Si₃N₄) substrate is >800MPa, providing anti-vibration support for MEMS inertial sensors and reducing signal drift caused by package deformation.
4. Anti-crack propagation capability
The fracture toughness KIC of zirconium oxide (ZrO₂) toughened ceramics can reach 12MPa, which inhibits microcrack propagation through phase transformation toughening mechanism and improves the reliability of high-temperature sensors under thermal shock.
5. Precision machining and surface quality
After laser machining and CVD surface treatment, the dimensional tolerance of the ceramic substrate is controlled at pm0.01mm, and the surface roughness Ra<0.1μm, ensuring the precise alignment and low contact resistance of the sensor electrodes.
6. Airtight packaging reliability
The ceramic shell leakage rate achieved by the HTCC process is <1×10-8Pa.m3/s, and there is no cracking after 1,500 times of -55℃-150℃ thermal shock test, meeting the IP67 protection requirements of automotive sensors.
Typical application cases:
Pressure sensor: Alumina shell has no fatigue cracks under 20kN cyclic load, which is used for fuel injection system monitoring.
Optical communication sensor: The displacement of silicon nitride substrate at 10GHz vibration frequency is <0.1 μm, ensuring the stability of optical fiber coupling.
Through material component optimization (Al₂O₃-ZrO₂ composite) and process innovation (hot isostatic pressing densification), ceramic packaging has achieved a reliability breakthrough in mechanical-thermal-electrical multi-field coupling scenarios.
Chapter 4 Miniaturization and Integration
1. High packaging density and miniaturized design
The ceramic shell realizes multi-layer wiring through HTCC process, with a wiring density of up to 200 lines/cm2. The CSOP package volume is only 2.5mm×2.0mm and weighs less than 0.1g. Kyocera’s AO700 material has a bending strength of 620MPa and supports thinner wall design (thickness <0.2mm).
2. Three-dimensional structure integration capability
The ceramic substrate uses DPC technology to manufacture a three-dimensional cavity structure, which supports the interference-free packaging of the movable parts of the MEMS sensor, and realizes the vertical stacking of the signal layer, power layer and ground layer, and the integration is increased by more than 3 times. CLCC package achieves high-density interconnection with 0.5mm pitch through four-sided T-shaped pins.
3. Precision machining and size control
Laser micromachining technology controls the size tolerance of ceramic substrates to pm0.01mm and the surface roughness Ra<0.1 μm, meeting the requirements of MEMS devices such as accelerometers for 10 μm-level structural accuracy.
4. Thermal expansion coefficient matching and low stress
The thermal expansion coefficient of aluminum nitride (AlN) ceramics is 4.5×10-6/℃, which is close to that of silicon chips (3×10-6/℃). After 1,500 thermal cycles, the interface delamination rate is <0.1%, ensuring the structural stability of miniaturized packaging.
5. High integration process compatibility
HTCC ceramic shell supports more than 8 layers of co-fired metallization, and the through-hole diameter can be reduced to 50 μm, realizing the miniaturized integration of complex circuits such as RF switch matrix. CPGA package integrates 1,200 pins through a multi-layer ceramic substrate with a density of 40 pins/cm2.
Typical application cases:
MEMS gyroscope: using three-dimensional ceramic substrate packaging, the size is reduced to 3mm×3mm, and the angular velocity accuracy reaches 0.01°/s.
Optical communication sensor: CQFN ceramic shell integrates microwave devices and optical coupling structure, the package thickness is <1mm, and supports 40GHz high-frequency signal transmission.
Through material component optimization (Al₂O₃-ZrO₂ composite ceramic) and process innovation (hot isostatic pressing densification), ceramic packaging continues to break through the technical limits in the field of miniaturization and high-density integration.
Chapter 5 Environmental protection performance
1. High air tightness and moisture resistance
The ceramic shell prepared by HTCC process has a leakage rate of <1×10-8Pa.m3/s, which can block moisture penetration (moisture absorption rate <0.02%), meet the IP67 protection level requirements, and is suitable for humid environments such as automotive sensors.
2. Chemical stability and corrosion resistance
Alumina (Al₂O₃) ceramics remain stable in strong acid (concentrated sulfuric acid) and strong alkali (NaOH solution) environments, with a corrosion rate of <0.01mg/cm²/year. Aluminum nitride (AlN) ceramics have no oxidation failure in high temperature (>600℃) sulfur-containing gas environments.
3. High temperature resistance and thermal shock performance
Zirconia (ZrO₂) ceramic shells maintain stable dielectric properties at 600^℃, and no cracking after 1,500 thermal cycles (-55℃-150^℃). Silicon nitride (Si₃N₄) substrates have a thermal shock resistance temperature difference of 800℃.
4. Mechanical protection capabilities
Alumina ceramics have a compressive strength of 2,500MPa and a flexural strength of 300MPa; the fracture toughness KIC of zirconia toughened ceramics reaches 12MPa, and can withstand a 20kN cyclic load.
5. Anti-electromagnetic interference shielding
The shielding effectiveness of the ceramic substrate reaches 60-80dB (@1GHz), and the square resistance of the surface metallization layer is <0.01Ω, which effectively suppresses the interference of electromagnetic noise on the sensor signal.
Typical application cases:
Automotive pressure sensor: The Al₂O₃ shell has a life of >10 years in a 150^℃ salt spray environment, and the leakage rate remains <5×10-9Pa.m³/s.
Industrial MEMS sensor: The capacitance drift of the AlN substrate is <0.5% in 85% humidity and 85℃ temperature tests.
Through material modification (Al₂O₃-ZrO₂ composite) and process optimization (hot isostatic pressing densification), ceramic packaging achieves breakthroughs in protection performance and reliability in extreme environments.
Chapter 6 New Sensor Technology
1. High-frequency and high-integration performance
The wiring density of the ceramic shell prepared by the HTCC process reaches 200 lines/cm2, and the diameter of the through hole can be reduced to 50 μm, which supports the integration of high-frequency circuits such as RF switch matrix. The CQFN package integrates microwave devices and optical coupling structures to support 40GHz high-frequency signal transmission.
2. Extreme environment adaptability
High temperature resistance: The dielectric properties of zirconium oxide (ZrO₂) ceramic shell are stable at 600℃, and the new thermal ceramic material (developed by the Chinese Academy of Sciences) has a suitable temperature range of -50^℃-1150^℃, and the aging drift rate is <1%.
Corrosion resistance: The corrosion rate of alumina ceramics in strong acid/alkali environments is <0.01mg/cm²/year, and the ceramic PCB oil level sensor can withstand the high temperature and high pressure environment of the engine.
3. High precision and stability
The ceramic pressure sensor has a hardness of 9GPa (Mohs), is resistant to shock and vibration, and has a long-term drift rate of <0.5% (double 85 test).
The temperature coefficient of thermistor ceramic resistance reaches 0.223%/K, which meets the monitoring needs of aerospace engines.
4. Heat dissipation and structural innovation
Zhongci Electronics’ patented CPGA tube shell integrates a heat sink block, which improves heat dissipation efficiency by 30% and supports high-power MEMS sensor packaging. The thermal conductivity of the aluminum nitride (AlN) substrate is 170-230W/(m·K), and the thermal expansion coefficient matches the silicon chip (4.5×10-6/℃), reducing thermal stress stratification.
Typical application cases:
Optical communication sensor: HTCC ceramic tube shell realizes 100Gbps optical signal transmission, and the leakage rate is <1×10-8Pa·m³/s.
Automotive oil level monitoring: Ceramic PCB sensor is based on piezoelectric effect, with a response time of <10ms and wear resistance 5 times higher than metal.
Chapter 7 Breakthrough Innovation
1. Wide temperature range and high-precision sensing
The new thermal ceramic material uses high entropy materials and a different price substitution strategy to achieve wide temperature range detection of -50℃-1150^℃, with an aging drift rate of <1% and a resistance temperature coefficient of 0.223%/K, which is suitable for high-precision scenarios such as aerospace engine monitoring.
2. Micro-resistance conduction and high heat dissipation efficiency
The patented design of Ceramic Gold Technology uses oxygen-free copper pillars to conduct components, reducing resistance loss by 30% and significantly improving conductivity efficiency; Zhongci Electronics CPGA shell integrated thermal Sink, heat dissipation efficiency increased by 30%, supporting high-power MEMS sensor packaging.
3. Breakthrough in single crystal materials and high-frequency performance
The single crystal β-CaSiO₃ substrate developed by Zefeng has a dielectric constant K<5, bending strength>230MPa, and supports 5G/6G high-frequency communication; the HTCC process achieves 40GHz high-frequency signal transmission, and the wiring density reaches 200 lines/cm².
4. Low-power integrated packaging
The MEMS gas sensor adopts QFN ceramic shell packaging, with power consumption as low as 10mW, micro-hotplate size 0.3mm², integrated nano SnO2 sensitive material, and detection accuracy increased by 3 times.
5. Extreme environment protection performance
The capacitance drift of AlN ceramic substrate is <0.5% under 85℃/85% humidity environment, the zirconia shell is resistant to 600℃ high temperature, 1,500 thermal cycles without cracking, and the leakage rate is <1×10-8Pa·m³/s.
6. Machinability and multi-dimensional integration
Macor machinable ceramics support stable operation at -200℃-800℃, with a surface roughness of Ra<0.1 μm. Combined with DPC technology, three-dimensional cavity packaging is achieved, and the integration level is increased by 3 times.
Through material innovation (high entropy ceramics) and process optimization (single crystal substrate preparation), semiconductor ceramic technology is driving sensors to leapfrog development in the direction of high frequency, high reliability, and miniaturization.
