Ceramic Substrate
A ceramic substrate is a ceramic-based substrate used in electronic packaging and power electronics. As circuit board producer, we focus on metal core printed circuit boards and ceramic substrate in circuit board production. With the increasing demand for high-performance electronic packaging, ceramic substrates have become an essential platform for thermal management and electrical interconnection. It is an electronic substrate prepared by using thermal conductive ceramic powder and organic adhesive under low temperature conditions (less than 250℃). As a key component widely applied in advanced packaging, sensing, actuation, and passive electronic applications.
Key features
| Key Property | Description |
|---|---|
| Dielectric Insulation & High Reliability | Provides excellent electrical insulation and ensures stable, long-term operation in demanding environments. |
| Low Dielectric Constant | Minimizes signal loss and supports superior high-frequency and RF performance. |
| Low Thermal Expansion Coefficient & High Thermal Conductivity | Enhances thermal management efficiency while reducing thermal stress caused by temperature fluctuations. |
| Good Airtightness & Chemical Stability | Offers strong environmental protection, corrosion resistance, and long-term durability for electronic systems. |
Ceramic substrate materials
Common types include alumina board (Al₂O₃), aluminum nitride (AlN), and silicon carbide(SiC) substrate, each with distinct properties tailored to specific applications. Standard 96% alumina substrate remain the dominant choice for electronics applications due to their cost-effectiveness and high reliability. These substrates are commonly manufactured through tape casting and high-temperature sintering process near 1600°C. They are the most commonly used in general electronic devices. Aln substrates stand out for their high thermal conductivity, making them ideal for power semiconductor devices like IGBT module and LED lighting control system where heat transfer properties are critical. Meanwhile, silicon carbide material offer superior structural stability and thermal stability, suitable for harsh environment applications such as aerospace and power automotive systems. These substrates provide a reliable platform for mounting and interconnecting electronic circuit board components, ensuring heat transfer coefficient and long-term operational stability. The low coefficient of thermal expansion also helps minimize thermal stress between components, enhancing the overall reliability of electronic assembly.
Wear resistance is considered as a system level characteristic rather than an isolated material property. The wear performance of ceramic materials is influenced by the mating surface, contact mechanism, operating conditions, lubrication, and applied stresses. Consequently, evaluating wear resistance requires consider multiple factors, Which include hardness, fracture toughness, surface finish, and environmental conditions, all of them contribute to the overall durability of the material in service.
The wear volume (V) is influenced by several factors, including the applied load (P), fracture toughness (KIc), hardness (H), and the number of abrasive particles (N) in contact with the surface. In general, materials with higher hardness and fracture toughness tend to exhibit better wear resistance, while higher loads and greater abrasive particle concentrations usually accelerate material loss.
How to Select Material?
Selecting the appropriate ceramic substrate material is essential for achieving optimal thermal performance, mechanical reliability, and cost efficiency in electronic applications. The choice typically depends on several key factors, including thermal conductivity, mechanical strength, thermal expansion behavior, and budget requirements. For applications requiring efficient heat dissipation, such as power modules, LED packaging, and electric vehicle electronics, aluminum nitride (AlN) is often preferred due to its high thermal conductivity and excellent electrical insulation. When mechanical reliability is a primary concern, particularly in environments involving thermal cycling, vibration, or mechanical stress, silicon nitride (Si₃N₄) is an ideal choice because of its superior fracture toughness and flexural strength. In applications where thermal expansion matching is critical, materials with lower coefficients of thermal expansion can help minimize thermal stress and improve long-term reliability. For cost sensitive applications, alumina (Al₂O₃) remains the most frequency used ceramic substrate material thanks to its low cost, mature manufacturing processes, and satisfactory overall performance. Other advanced ceramics, such as beryllium oxide (BeO), may be selected when extremely high thermal conductivity is required, although their use is more limited due to safety and environmental considerations. In general, alumina is favored for cost-effective solutions, aluminum nitride for superior thermal management, and silicon nitride for demanding high-reliability applications. This selection approach helps engineers balance performance, durability, and manufacturing costs.
Manufacturing Process
DPC technology
The DPC process uses vacuum sputtering to deposit Ti/Cu seed layers on the surface of ceramic substrates, and then completes the circuit production through manufacturing process photolithography, development, etching, and electroplating/chemical plating. This process is a low temperature process (below 300 °C), which reduces manufacturing costs and enables fine circuits. (Line width 20~30μm, alignment accuracy error less than ±1%). The disadvantages of DPC include limited thickness of the electroplated copper layer, low bond strength between ceramic and metal, and pollution of electroplating waste liquid. DPC substrates are suitable for electronic devices with high precision requirements, such as LED lights, semiconductor lasers, IGBT, LD, and CPV packaging.
AMB technology
AMB technology is development of DBC technology. By accessing strong metal ceramic bonding at reduced processing temperatures, active metal brazing (AMB) effectively decreases residual thermal stress and improves the reliability of ceramic substrate assemblies. Compared with traditional DBC substrates based on Al₂O₃, AMB substrate utilize chemically metallic bonding ceramic interfaces and highly silicon conductivity ceramics to achieve enhanced thermal performance, electrical insulation, and mechanical properties. The ability to support higher power density has led to widespread adoption in electric vehicle technology and other demanding power electronics industrial applications.
DBC technology
DBC substrate is commonly used in air condition, refrigerator and low and medium consumer electronics. Direct bonded copper (DBC) substrates primarily use al2o3 and aln ceramic. Alumina oxide ceramic is the mainstream choice in the industry because it combines mature manufacturing technology with cost-effective production, accounting for about 80% of DBC substrates available on the market.
LTCC and HTCC
Ceramic firing process differ significantly between HTCC and LTCC systems. HTCC is typically sintered at temperatures up to around 1600 °C in a reducing atmosphere, while LTCC is processed at a much lower temperature, around 875 °C, under an oxidizing atmosphere. In terms of metallization, HTCC generally requires post-firing surface finish such as nickel plating or Ni/Au plating to enable reliable interconnections. In contrast, LTCC material systems inherently support soldering and bonding application more directly. In addition, Ag conductor lines with plating are commonly used as a mature solution to ensure good solderability and bond performance. Furthermore, passive integral component such as embedded resistors, is mainly feasible within LTCC technology, whereas it is not typically supported in HTCC structures. LTCC packaging solutions can be clearly differentiated from other technologies by several key advantages. Compared with organic packaging approaches, LTCC offers significantly higher reliability. In contrast to conventional thick-film technology, it enables a much higher level of miniaturization. When compared with HTCC, LTCC provides enhanced functional integration, while against semiconductor-level integration it requires only a fraction of the development effort and tooling cost. In terms of manufacturing capabilities, current LTCC technology can achieve line and spacing resolutions below 100 µm, with via diameters around 100 µm and via spacing of approximately 150 µm. It also allows partial monolithic integration of passive components such as resistors, capacitors, and inductors within the substrate, although within limited value ranges. In addition, LTCC supports true 3D integration, enabling the incorporation of fluidic structures such as microchannels and reaction chambers directly into the package architecture.
How to Decide Manufacturing Method?
| Feature | DBC (Direct Bonded Copper) | AMB (Active Metal Brazing) | DPC (Direct Plated Copper) |
|---|---|---|---|
| Metal line width | ≥200 μm | ≥100–200 μm (typical) | <50 μm |
| Copper thickness | 120–700 μm | 100–1000 μm (300 μm+ typical) | 10–150 μm |
| Bonding strength / reliability | Good copper-ceramic bonding, suitable for power applications | Excellent thermal cycling reliability and strong ceramic-metal bonding | High adhesion strength between copper layer and ceramic substrate |
| Electrical performance | Low electrical resistance due to thick copper layer | Excellent current carrying capability for high-power devices | Low resistance with fine circuit patterns |
| Manufacturing characteristics | Mature and cost-effective process | More complex than DBC but provides better reliability | Requires precision sputtering, photolithography, and electroplating equipment |
| Suitable ceramic materials | Mainly Al₂O₃ and AlN | AlN, Si₃N₄, and Al₂O₃ | Al₂O₃, AlN, and other ceramics |
| Suitable applications | IGBT modules(tradition), power electronics, high-current devices | IGBT modules(EV), SiC power devices, EV inverters, high-reliability power systems | High-power LEDs, deep ultraviolet (DUV) LEDs, RF and miniaturized electronic devices |
| Main advantages | Thick copper layer, high current capacity, mature technology | Superior reliability and thermal cycling performance | Fine circuit resolution and excellent thermal/electrical performance |
| Main limitations | Limited circuit resolution | Higher cost and limited fine-line capability | Higher equipment cost and thinner copper layer |
Direct Plated Copper (DPC) technology provides high circuit resolution, strong copper ceramic bonding strength, and low electrical resistance. By combining photolithography and electroplating process, it can achieve fine copper line below 50 μm. Regarding electrical and mechanical properties, the sputtered copper layer exhibited a tensile strength of 3.0 MPa and a sheet resistance of 0.101 Ω·cm/sq, while deposited copper layers showed a sheet resistance of 0.334 Ω·cm/sq. Currently, DPC technology is primarily applied in high power LED packaging. For high brightness led and deep ultraviolet (DUV) LEDs operating under high heat generation conditions. However, environmental regulations and restrictions on electroplating process in many regions have indirectly affected the development and large scale adoption of DPC technology. In addition, the high cost of precision sputtering equipment required for DPC fabrication increases the overall manufacturing cost. Therefore, further development of DPC technology is needed to improve copper layer thickness, reduce production costs, and enhance its competitiveness in advanced electronic packaging applications.
Direct Bonded Copper (DBC) technology requires specific ceramic PCB due to the limited wettability of molten copper. Pure copper shows poor wettability on Al₂O₃, AlN, and Si₃N₄, with contact angles exceeding 130°. Increasing oxygen partial pressure during bonding and introducing oxygen into the copper melt can significantly improve copper wettability on Al₂O₃. For AlN substrate, methods such as increasing oxygen pressure, vacuum bonding, and extending bonding time provide limited improvement. Therefore, AlN is usually pre-oxidized to form an Al₂O₃ layer on the surface before DBC bonding. However, these approaches are ineffective for improving copper wettability on Si₃N₄, making DBC rarely applicable to Si₃N₄ substrates. Copper layers with thicknesses of DBC ranging from 120 μm to 700 μm, while wet etching processes can achieve circuit widths of approximately 200 μm. High-quality DBC substrate show strong copper ceramic bonding strength above 65 N/cm. However, the relatively large circuit width limits their application in high density electronic devices. In addition, substrate compatibility issues and limited thermal cycling reliability also restrict their use in high power application. The resolution limitations of wet etching further hinder the adoption of DBC substrate in miniaturized electronic packaging.
Active Metal Brazing (AMB) is a reliable metal processing for high power electronics. Compared with DBC, AMB uses active brazing alloys (such as Ag-Cu-Ti) to achieve stronger bonding between copper and ceramic substrates, enabling better thermal cycling reliability. It is mainly applied in IGBT module, SiC power devices, EV inverters, and other high power systems. AMB substrates typically use thicker copper layers (up to 300 μm or more) and are compatible with AlN and Si₃N₄ ceramics. However, similar to DBC, AMB still faces limitations in circuit resolution, which restricts its application in highly miniaturized electronic devices.