LTCC, which stands for Low Temperature Co-fired Ceramic, is, as the name suggests, a technology that co-fires multilayer ceramic materials with metallic conductors at relatively low temperatures (typically below 900°C). Since its development by Hughes Corporation in the United States in 1982, this technology has evolved from its initial application in radar chips to form complex microelectronic systems.
Characteristics of LTCC Technology
Low-temperature sintering: LTCC employs a co-firing process for ceramic powders and metallic pastes at temperatures below 900°C, thereby reducing production costs and energy consumption.
Multilayer Integration: Raw ceramic tape prepared via roll-to-roll forming undergoes laser drilling, conductor paste printing, and laminated hot pressing to form electronic substrates with embedded three-dimensional circuit networks. This technology supports the integration of multiple passive components, enhancing circuit assembly density and functional diversity.
Diverse Material Selection: LTCC technology accommodates metallic electrodes such as silver and copper, with a broad dielectric constant range (4.8 to 70), combining high-frequency transmission characteristics with thermal stability.
Discontinuous Production: Facilitates quality inspection of each layer’s wiring and interconnect vias prior to final assembly, improving multilayer substrate yield and quality while shortening production cycles and reducing costs.
Key Advantages of LTCC Technology
Superior High-Frequency Performance: LTCC materials exhibit outstanding high-frequency characteristics and high-speed transmission capabilities. Their ceramic composition delivers high Q-factor and stable dielectric constants, which can be tailored through formulation adjustments to meet diverse circuit requirements, thereby enhancing design flexibility. Furthermore, employing high-conductivity metals such as silver and copper as conductors enhances the quality factor of circuit systems. This renders LTCC particularly effective in high-frequency applications including microwave and millimetre-wave technologies.
High Integration and Miniaturisation: LTCC technology enables high-density routing and structural configurations, allowing multiple passive components (resistors, capacitors, inductors, filters, etc.) to be embedded within multilayer substrates. This substantially increases circuit assembly density, enables multifunctionality, and significantly reduces the volume and weight of electronic modules. It can also be integrated with active components to form complete circuit systems, making it the mainstream technology for passive integration.
High reliability and environmental adaptability: LTCC substrates exhibit excellent resistance to high temperatures and large currents, with thermal conductivity superior to conventional PCB boards. This endows LTCC products with extended service life and heightened reliability, rendering them particularly suitable for demanding environments such as automotive electronics, aerospace, and military applications. Furthermore, their thermal expansion coefficient matches that of silicon chips, reducing thermal stress and contributing to the reliability of high-density packaging. LTCC also possesses excellent hermeticity, safeguarding internal components from moisture and chemical corrosion.
Cost-effectiveness and production efficiency: LTCC employs a low-temperature sintering process (typically below 900°C), which reduces equipment requirements and permits the use of lower-cost conductor materials such as silver and copper. The discontinuous production process facilitates quality inspection of each layer prior to sintering, thereby enhancing multilayer substrate yield, shortening production cycles, and lowering overall costs.
Design Flexibility and Multifunctionality: LTCC technology enables the integration of multiple functions, such as embedding passive components like resistors, capacitors, and inductors. It also permits the creation of cavities with diverse geometries, facilitating the development of high-performance multifunctional microwave modules. LTCC exhibits excellent compatibility with thin-film multilayer wiring technology; their combined use enables hybrid multi-chip modules with higher assembly density and superior performance.
The demand for LTCC (Low-Temperature Co-fired Ceramic) technology stems from its irreplaceable advantages in modern electronic systems. Particularly under trends towards high frequency, high speed, high integration, and miniaturisation, its characteristics become pivotal in overcoming limitations of conventional technologies.
Why is LTCC required?
1.The inevitable choice for high-frequency communications
Superior high-frequency performance: With the advancement of technologies like 5G, 6G, and millimetre-wave communications, signal frequencies are leaping to the GHz and even THz levels. Conventional materials (such as FR-4) exhibit significantly increased losses at high frequencies. Conversely, LTCC’s dielectric constant (εr) and loss tangent (tanδ) can be precisely tuned through material formulation, enabling low loss and high Q-factor to meet high-frequency signal transmission demands.
Integrated Filters: LTCC allows embedding of passive components like 3D filters and duplexers, reducing signal path losses and enhancing communication module performance. For instance, filter arrays in 5G base stations employing LTCC technology can achieve over 50% volume reduction while simultaneously lowering insertion loss.
2.Demand for Miniaturisation and High Density
Multi-layer routing capability: LTCC supports routing across ten or more layers, with interlayer connections achieved via laser drilling. Vertical interconnect density can reach hundreds of vias per square millimetre, far surpassing traditional PCB circuit board technology. This substantially increases functional integration in space-constrained applications such as mobile phones and wearable devices.
Embedded Component Technology: Passive components including resistors, capacitors, and inductors can be directly embedded within LTCC substrates, reducing surface-mount component counts and saving space. For instance, smartphone antenna modules incorporating LTCC achieve a 30% volume reduction while enhancing antenna efficiency.
3.Reliability and Environmental Adaptability
High-Temperature and Thermal Cycling Resistance: LTCC substrates exhibit excellent dimensional stability across the -55°C to +125°C temperature range. Their coefficient of thermal expansion (CTE) matches semiconductor chips, minimising failures caused by thermal stress. This property is critical in automotive electronics (e.g., ADAS sensors) and aerospace applications.
Hermetic Sealing: it enables co-firing with metals and ceramics to form airtight chambers, shielding internal components from moisture, corrosion and other environmental factors to extend product lifespan. For instance, LTCC encapsulated modules in medical implants achieve lifespans exceeding 10 years.
4.Balancing Cost and Production Efficiency
Low-temperature sintering process: Sintering temperatures below 900°C enable compatibility with low-cost conductive materials like silver and copper, reducing raw material expenses. Concurrently, the low-temperature process minimises energy consumption, shortens production cycles, and enhances manufacturing capacity.
Discontinuous production: it supports layer-by-layer inspection, allowing early detection and rectification of defects. This yields a yield rate over 20% higher than traditional high-temperature co-fired ceramics (HTCC), thereby lowering overall costs.
5.Driving Cross-Domain Technology Convergence
Compatibility with Thin-Film Technology: LTCC integrates with thin-film processes to form hybrid multilayer substrates, balancing high-frequency performance with fine-pitch routing. For instance, in optical modules, it supports high-speed optoelectronic devices while thin-film layers enable micron-scale interconnections.
Support for System-in-Package (SiP): As a substrate material for SiP, it enables integration of diverse functional modules such as sensors, MEMS, and ICs, driving the development of miniaturised systems in fields like the Internet of Things and autonomous driving.
LTCC technology, with its high-frequency performance, high integration density and environmental adaptability, effectively meets the demand for miniaturised, high-performance electronic components in fields such as 5G communications and automotive electronics. As materials and processes continue to be optimised, its scope of application will expand further, providing stable support for the reliable operation and functional integration of electronic systems, thereby becoming a significant driving force for technological advancement within the industry.
