Automotive industry’s three new development trends refer to electrification, intelligence (including networking) and sharing.
Ceramic PCB is a substrate formed by copper-clad technology on a ceramic substrate; and then is made by laser drilling, pattern etching and other processes. According to the process, ceramic substrates are mainly divided into DBC, AMB, DPC, HTCC, LTCC and other substrates. Based on the substrate materials, they are mainly divided into alumina (Al2O3), aluminum nitride (AlN) and silicon nitride (Si3N4).
Among them, alumina ceramic substrate is the most commonly used, mainly adopting DBC process; aluminum nitride ceramic substrate has high thermal conductivity, mainly adopting DBC and AMB process; silicon nitride has excellent reliability, mainly adopting AMB process. The ceramic liner produced by the AMB process is mainly used on the power semiconductor module as the substrate of silicon-based and carbon-based power chips.
Accelerate to introduce the SiC electrification platforms
Mainstream new energy enterprises are accelerating the introduction of high-voltage SiC platforms. From 2021 to 2022, other countries’ brands such as Hyundai IONIQ5, Audi e-tron GT, and Porsche Taycan, as well as China models such as Beiqi Polar Fox Alpha have taken the lead in applying 800V high-voltage platform and SiC power module.
After 2023, more new energy vehicles based on 800V architecture will enter the mass production stage. It’s estimated that, by 2025, the proportion of SiC technology used in the field of automotive electronic power devices will exceed 20%.
When the voltage rises to 800V, the withstand voltage level of the corresponding power device needs to be raised to 1200V. According to the test of Times Electric, when the bus voltage reaches 785V and the output power is above 190kW, the total loss of the 1200V SiC inverter reaches 360.5w. While, the total loss of the 1200V IGBT device reaches 783.5w, and the SiC device reduces the loss by 54% compared with the IGBT.
Under typical high output power conditions, the inverter efficiency of the 1200V SiC device reaches 98.77%, and that of the IGBT reaches 97.5%. From the perspective of the loss distribution, the switching loss of the IGBT device is significantly higher than that of the SiC device, and nearly 56% of the loss of the IGBT occurs in the switch Loss, SiC switching loss accounted for only 48.5%.
Under the condition of low output power, the total inverter loss of the 1200V SiC device is 54.8W, while that of the 1200V IGBT device is 193.9W, and the loss of the SiC device is 71.7% lower than that of the IGBT device. The switching loss and on-state loss of SiC devices compared with IGBT devices have dropped significantly.
As the voltage level of new energy vehicles rises to 800V, the power module of the main drive inverter begins to be replaced by silicon carbide, and AMB-silicon nitride substrates become popular. STMicroelectronics, BYD Semiconductor and Times Electric have all determined the technical route for AMB silicon nitride substrates.
Demand for AMB enters accelerated growth period
Among the ceramic substrate subdivision processes, the compound growth rate of the AMB substrate market is the fastest, with a CAGR of 25% from 2020 to 2026. The AMB process will gradually become mainstream due to its better reliability.
According to statistics, the aluminum nitride ceramic substrate (AMB-AlN) using the AMB process is mainly used in high-voltage, high-current power semiconductors such as high-speed rail, high-voltage converters, and DC power transmission; the silicon nitride ceramic substrate (AMB-AlN) using the AMB process -SiN) is mainly used in electric vehicles (EV) and hybrid vehicles (HV) power semiconductors.
AMB-SiN ceramic substrate has high thermal conductivity, high current carrying capacity and low thermal expansion coefficient, and its superior performance is expected to become a new trend in the application of IGBT and SiC power device substrates:
1) High thermal conductivity, high current carrying capacity:
The thermal conductivity of the AMB-SiN ceramic substrate is higher than 90W/mk, and the thick copper layer has high heat capacity and heat transfer performance. At the same time, the AMB process can weld thick copper metal (800μm) to relatively thin silicon nitride ceramics, forming a high current-carrying capacity.
2) Low thermal expansion coefficient:
The thermal expansion coefficient of AMB-SiN ceramic substrate is 2.4ppm/K, which is close to silicon chip (4ppm/K), has good thermal matching, and is suitable for reliable packaging of bare chips.
AMB substrates account for nearly 10% of the cost of power modules. Therefore, it’s reported that the global SiC power device market size will increase from US$1.09 billion to US$6.297 billion in 2021-2027. Besides, it’s estimated that the global AMB substrate market driven by SiC power devices will grow from US$109 million to US$630 million in 2021-2027.
AMB better substitutes DBC in high-power IGBT modules
In traditional IGBT modules, the alumina precision ceramic substrate is the most commonly used precision ceramic substrate, which has good insulation, chemical stability, mechanical properties and low price. However, due to the relatively low thermal conductivity of alumina precision ceramic substrates and poor matching with the thermal expansion coefficient of silicon, they are not suitable as packaging materials for high-power modules.
At present, DBC ceramic substrates are mainly used for IGBT packaging. The reason is that DBC has a large metal layer thickness (generally 100~600um) with large current carrying, good high-temperature resistance and high reliability, and good thermal shock resistance.
AMB technology realizes the bonding of aluminum nitride and silicon nitride ceramics and copper sheets, which can greatly improve the reliability of ceramic substrates, and has gradually become the main application type of heat dissipation circuit boards for mid-to-high-end IGBT modules.
Currently, Si-based IGBT modules are gradually adopting AMB ceramic lining boards to replace the original ones in rail transit, industrial grade, and automotive grade fields that require high thermal conductivity, high reliability, and high power, and are not sensitive to cost.
The penetration rate of silicon carbide will increase rapidly
The penetration rate of silicon carbide vehicles is expected to increase rapidly in 2024, and the field of new energy vehicles will become the largest demand field for AMB ceramic substrates. Tesla is the world’s largest consumer of silicon carbide modules. Model 3 has been equipped with silicon carbide MOSFET modules as standard instead of IGBTs as inverter power devices. All silicon carbide modules must use AMB-silicon nitride ceramic packaging materials.
The current unit price of a standard liner is about 400 RMB. It is estimated that the global adoption of SiC models will reach 10.32 million in 2027. Considering that the price will be reduced to about 300 RMB in the future, it is predicted that the SiC car market size will reach 3.43 billion RMB in 2027. If the car-grade IGBT modules above 750V are also replaced, the AMB substrate market space required for car-grade electronic control modules will reach about 5 billion RMB.
The global AMB ceramic substrate market is expected to grow to 8.95 billion RMB in 2027: AMB ceramic substrates have been used in high-power IGBT module packaging in industrial fields due to their excellent thermal conductivity and bending strength, such as power grids and motor vehicles.
In addition, the military and aerospace fields have higher requirements for high reliability of devices and lower cost sensitivity, so AMB ceramic substrates are currently widely used, and it is possible to replace PCBs as chip packaging substrate materials in the future.
Considering the heavy volume in the field of new energy vehicles and the continued growth in demand in the fields of superimposed industry, military industry and photovoltaics, the global demand for AMB substrates will reach about 9 billion RMB in 2027.
Insufficient Chinese AMB suppliers stimulate production expansion
AMB substrate suppliers are still mainly dominated by European, American, Japanese and Korean companies, such as Rogers, KCC, Heraeus, and Dowa. These enterprises have leading production technology and occupy a major market share. At present, Chinese AMB ceramic lining boards mainly rely on imports because the production capacity is relatively small.
As SiC MOS begins to supply main drive inverters, the production capacity consumption of ceramic liners increases rapidly due to the larger area of SiC MOS required for inverters.
SiC MOSFET single chip and electronic control module packaging in the OBC field also require AMB-silicon nitride substrates. Domestic new energy OEMs (Great Wall, BAIC, BYD, Xiaopeng, etc.) have successively introduced 800V electrification platforms, and domestic manufacturers are expected to benefit from supporting R&D advantages and local service advantages to accelerate domestic substitution.
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