LTCC PCB

The application and technical characteristics of LTCC PCB

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LTCC (Low Temperature Co-fired Ceramic) refers to a process where multiple layers of ceramic green sheets, printed with conductive metal patterns and interconnected vias, are stacked together after precise alignment and then co-fired at temperatures below 900°C to form a monolithic multilayer interconnect structure.

This technology allows for increased wiring density and shorter interconnect distances, as well as the independent design of circuits on each layer of the substrate, enabling the realization of circuits with three-dimensional structures.

Additionally, the surface of the multilayer ceramic substrate can be used to mount bare chips by cavity mounting or to install other circuit components by surface mounting, utilizing inter-layer vias and internal circuits for connectivity. This greatly enhances the assembly density of circuits, meeting the requirements of electronic devices for circuit miniaturization, high density, multifunctionality, high reliability, and high transmission rates.

Applications of LTCC PCB

LTCC PCBs are widely used in various applications that require high performance, reliability, and operation in harsh environments. Some key application areas include:

  1. Aerospace and Defense: LTCC multilayer ceramics are used in aerospace electronic systems, radar systems, missile guidance systems, and other military applications that require high reliability, resistance to harsh environments, and high-frequency performance.

  2. Automotive Electronics: The excellent thermal performance and reliability of LTCC PCBs make them suitable for automotive applications, such as engine control units, sensors, and Advanced Driver Assistance Systems (ADAS).

  3. Telecommunications: LTCC technology is widely used in high-frequency applications in the telecommunications industry, such as RF front-end modules, power amplifiers, and antenna arrays for cellular base stations and satellite communications.

  4. Medical Devices: The biocompatibility and hermetic sealing capability of LTCC PCBs make them suitable for implantable medical devices, such as pacemakers, cochlear implants, and neurostimulators.

  5. Industrial Sensors and Controls: LTCC multilayer ceramics are used in various industrial applications due to their ruggedness and tolerance to extreme temperatures, vibrations, and chemicals. This includes pressure sensors, flow meters, and harsh environment monitoring systems.

Manufacturing Process of LTCC PCB

The production process of Low Temperature Co-fired Ceramic (LTCC) PCB typically involves the following steps:

  1. Film Removal: Remove the film layer on the surface of the glass fiber board, usually done using an alkaline solution.

  2. Drilling: Punch holes on the ceramic board according to the requirements of the circuit diagram.

  3. Shaping: Mold solder pads and component positions on the ceramic board according to the requirements of the PCB.

  4. Coating: Apply coating on the surface of the shaped PCB to enhance its mechanical strength.

  5. Sintering: Subject the coated PCB to high-temperature sintering to achieve ceramicization and hardening of the PCB.

  6. Processing: Perform processes such as adhesive application and cleaning.

Material Selection for LTCC PCB

The materials used in the fabrication of LTCC PCBs include circuit layers, inner layer vias, hook holes, solder resist films, ceramic powders, silicon nitride, etc. Among them, ceramic powder is the primary raw material for making LTCC PCBs. The quality and performance of the selected ceramic powder determine the reliability and stability of the PCB. It is recommended to choose high-purity ceramic powder to ensure that the produced PCB has sufficient mechanical strength and durability.

Testing Specifications for LTCC PCB

The produced LTCC PCBs need to undergo relevant tests to ensure their quality and stability. The main testing specifications include:

  1. Solderability Test: Assessing the soldering quality of solder pads and wires on the PCB.

  2. Insulation Resistance Test: Measuring whether the insulation resistance of the PCB meets specified requirements.

  3. Metal Adhesion Test: Evaluating the adhesion between the conductive layer on the PCB surface and the ceramic substrate.

  4. Thermal Shock Test: Assessing the stability and reliability of the PCB under rapid temperature changes.

  5. Low-Temperature Constant Stress Test: Evaluating the stability and reliability of the PCB under specified temperature and stress conditions.

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Advantages of LTCC Integration Technology

Technological Advantages:

  1. Ceramic materials possess excellent high-frequency, high-speed transmission, and wide bandwidth characteristics. Depending on the composition, the dielectric constant of LTCC materials can vary within a wide range. When combined with high-conductivity metal materials as conductors, it helps improve the quality factor of the circuit system, increasing the flexibility of circuit design.

  2. LTCC can meet the requirements of high current and high temperature resistance, and it has better thermal conductivity than ordinary PCB circuit substrates. This greatly optimizes the thermal design of electronic devices, enhances reliability, and can be applied in harsh environments, extending their service life.

  3. It can produce circuit boards with a high number of layers, and multiple passive components can be embedded within them, eliminating the cost of packaging components. On high-layer three-dimensional circuit boards, integration of passive and active components facilitates increased circuit assembly density, further reducing volume and weight.

  4. It has good compatibility with other multilayer wiring technologies. For example, combining LTCC with thin-film wiring technology can achieve hybrid multilayer substrates and hybrid multi-chip components with higher assembly density and better performance.

  5. Discontinuous production processes facilitate quality inspection of each layer of wiring and interconnection holes before final product assembly. This helps improve the yield and quality of multilayer boards, shorten production cycles, and reduce costs.

  6. Energy saving, material saving, green, and environmental protection have become irresistible trends in the component industry, and LTCC meets this development demand. It minimizes environmental pollution caused by raw materials, waste, and production processes to the greatest extent.

Application Advantages:

  1. Easy to achieve more wiring layers, increasing assembly density.

  2. Convenient for embedding components internally, enhancing assembly density and achieving multifunctionality.

  3. Facilitates quality inspection of each layer of wiring and interconnection holes before substrate firing, which is beneficial for improving the yield and quality of multilayer boards, shortening production cycles, and reducing costs.

  4. Exhibits excellent high-frequency and high-speed transmission characteristics.

  5. Easy to form various structures of cavities, thus enabling the realization of high-performance multifunctional microwave MCMs (Multichip Modules).

  6. Possesses good compatibility with thin-film multilayer wiring technology. Combining the two can achieve hybrid multilayer substrates and hybrid multichip components (MCM-C/D) with higher assembly density and better performance.

  7. Easy to realize integration of multilayer wiring and packaging, further reducing volume and weight, and improving reliability.

Technical Features:

Utilizing LTCC for the fabrication of chip-type passive integrated devices and modules offers several advantages:

  1. Ceramic materials exhibit excellent high-frequency and high Q-factor characteristics.

  2. The use of high-conductivity metal materials as conductor materials helps improve the quality factor of the circuit system.

  3. It can adapt to high current and high-temperature requirements and possesses better thermal conductivity than ordinary PCB circuit boards.

  4. Passive components can be embedded into multilayer circuit boards, facilitating increased circuit assembly density.

  5. It has favorable temperature characteristics, such as a small coefficient of thermal expansion and a small temperature coefficient of dielectric constant, allowing for the production of extremely high-layer circuit boards and structures with line widths smaller than 50μm. Additionally, the discontinuous production process allows for inspections of the green substrate, thereby enhancing yield and reducing production costs.

The future development trends of LTCC technology, as an advanced passive component miniaturization technique, will focus on further enhancing integration, miniaturization, high-frequency capability, and reliability. With the increasing demand for high-performance and high-reliability electronic products in fields such as electronics, communications, and automotive industries, LTCC technology is expected to play a crucial role in more application scenarios, driving sustained and stable market growth. Additionally, with technological advancements, the layer count of LTCC technology may further increase, enabling more efficient circuit designs and superior performance.