Circuit substrates are the fundamental raw materials for the information industry. Since the practical application of copper-clad laminates made from phenolic resin substrates in 1943, the development of substrate materials has been very rapid. Circuit boards can be roughly divided into three categories: polymer circuit boards (printed circuit boards), metal circuit boards (metal boards), and ceramic circuit boards.

Next, let's focus on understanding ceramic circuit substrates:

Ceramic substrate refers to a special process board where copper foil is directly bonded to the surface of a ceramic substrate (single or double-sided) at high temperature. The ultra-thin composite substrate produced has excellent electrical insulation performance, high thermal conductivity, excellent brazing performance, and high adhesion strength. It can also etch various patterns like a PCB board and has great current carrying capacity. Therefore, ceramic substrates have become the fundamental material for high-power power electronic circuit structure technology and interconnection technology.

Introduction to Ceramic Substrates

Aluminum oxide ceramic substrate is a relatively early ceramic substrate, and its development trend has always been good. In 2015, the domestic production of alumina ceramic substrates (thermal conductivity of 25W/m · K) exceeded 2 million square meters, accounting for approximately 10% of the world's total production.

Aluminum nitride ceramic substrates have demonstrated superior performance on the basis of aluminum oxide. In 2015, the domestic production of aluminum nitride ceramic substrates (thermal conductivity of 200W/m · K) was about 5000 square meters, accounting for about 0.1% of the world's total production.

In existing technologies, it is generally believed that silicon nitride has a low thermal conductivity, so it is not suitable as a circuit substrate. However, in recent years, improvements made to improve the thermal conductivity of silicon nitride ceramics have been disclosed in Japan's authorized publication 135771/1994, and silicon nitride ceramics with a thermal conductivity of approximately 120W/MK have been obtained.

2. Characteristics of Ceramic Substrates

Ceramic electronic substrates have strong mechanical stress and stable shape; High strength, high thermal conductivity, and high insulation; Strong adhesion and corrosion resistance; Has excellent thermal cycling performance, with 50000 cycles and high reliability; A structure that can etch various shapes like a PCB board (or IMS substrate); Non polluting and pollution-free.

But its output is extremely low. Due to manufacturing technology and process research and development costs, the unit price of high-end new ceramic substrates is now higher. However, the production process and product itself are completely environmentally friendly. After the technical bottlenecks and trade barriers are broken, the price will significantly decrease with the increase of production, which is the future development direction of electronic circuit substrates.

3. Advantages of Ceramic Substrates

The thermal expansion coefficient of ceramic substrates is close to that of silicon chips, which can save transition layer Mo chips, save labor, materials, and reduce costs; Reduce welding layer, reduce thermal resistance, reduce voids, and improve yield;

Under the same current carrying capacity, the wire width of 0.3mm thick copper foil is only 10% of that of ordinary printed circuit boards; Excellent thermal conductivity makes the packaging of chips very compact, greatly increasing power density and improving the reliability of systems and devices;

Ultra thin (0.25mm) ceramic substrate can replace BeO, with no environmental toxicity issues;

High current carrying capacity, 100A current continuously passes through a 1mm wide and 0.3mm thick copper body, with a temperature rise of about 17 ℃; A 100A current continuously passes through a 2mm wide and 0.3mm thick copper body, with a temperature rise of only about 5 ℃;

Low thermal resistance, 10 × The thermal resistance of a 10mm ceramic substrate is 0.63mm. The thermal resistance of a 3mm thick ceramic substrate is 0.31K/W, the thermal resistance of a 0.38mm thick ceramic substrate is 0.19K/W, and the thermal resistance of a 0.25mm thick ceramic substrate is 0.14K/W;

High insulation and voltage resistance, ensuring personal safety and equipment protection capability.

4. Performance requirements for ceramic substrates

Mechanical properties: It has sufficient high mechanical strength and can be used as a supporting component in addition to carrying components; Good processability and high dimensional accuracy; Easy to achieve multi-layer; Smooth surface, without warping, bending, microcracks, etc.

Electrical properties: high insulation resistance and insulation failure voltage; Low dielectric constant; Low dielectric loss; Stable performance under high temperature and humidity conditions, ensuring reliability.

Thermal properties: high thermal conductivity; Matching the thermal expansion coefficient with relevant materials (especially with the thermal expansion coefficient of Si); Excellent heat resistance.

Other properties: Good chemical stability; Easy to metallize, circuit graphics have strong adhesion to them; No hygroscopicity; Oil and chemical resistance; α Low radiation emission; The substances used are pollution-free and non-toxic; The crystal structure remains unchanged within the temperature range of use; Rich raw materials; Mature technology; Easy to manufacture; The price of ordinary ceramic substrates is low.

5. Key markets at present

Electric vehicles, subways, and high-speed trains: The 18 country alliance of Germany, Norway, and the United States has announced a ban on the production and sales of gasoline powered vehicles by 2030, which is beneficial for electric vehicles. The national the Belt and Road strategy is beneficial to the high-speed rail market. National urbanization construction is beneficial for the urban rail transit market. The domestic market for ceramic substrates for electric vehicles exceeds 10 billion yuan per year.

Semiconductor refrigeration: Semiconductor refrigeration chips can be used for temperature control and thermoelectric power generation, and the ceramic substrate market for semiconductor refrigeration chips now exceeds 100 million yuan per year.

LED lighting: On New Year's Day 2014, the US government legislated to ban the production and sale of incandescent bulbs, leading to an explosion in the LED market. Blue light LED research won the Nobel Prize in Physics in 2014. The research on silicon-based LED lighting won the first prize of China's National Technology Invention Award in 2014. The domestic market for LED lighting ceramic substrates exceeds 20 billion yuan per year.

5G Communication: Huawei and ZTE have listed semiconductor refrigeration technology as a key supporting technology for 5G communication equipment and terminals. It is expected that the market for high-efficiency heat dissipation technology products will experience explosive growth in the 5G communication market, with an expected annual output of over 5 billion yuan. The future technological hotspots of information industries such as cloud computing, big data, artificial intelligence, autonomous driving, and robotics all require strong support from high-performance ceramic electronic circuit substrate materials.

5. Development trends of ceramic substrates

The emergence of ceramic substrate products has opened up the development of the heat dissipation application industry. Due to the unique heat dissipation characteristics of ceramic substrates, coupled with the advantages of high heat dissipation, low thermal resistance, long service life, and voltage resistance, with the improvement of production technology and equipment, product prices are accelerating and rationalizing. The future market area of this industry should be very broad.