The new generation of industrial parts is alumina ceramics, which will replace traditional metal parts, because ceramics have good performance and high availability, which can further improve the performance of the machine.
High-purity alumina ceramics can be made into molten laminated glass to replace platinum tongs pots, and can also be used as high-pressure sodium lamp tubes with its light transmittance and resistance to alkaline earth metal corrosion; 99 alumina porcelain raw materials are key to making high-temperature tongs pots , Fire-proof furnace body and unique metal composite materials, such as porcelain hydraulic seals, water inlet valves and ceramic bearings; 95 alumina porcelain is mainly used as corrosion-resistant and wear-resistant parts; 85 porcelain is often mixed with some talc to improve For electrical performance and mechanical strength, it can be sealed with metals such as molybdenum, niobium, and tantalum, and some are used as electrical vacuum devices.
Aluminum oxide production and processing, good insulation properties at room temperature and high temperature, low impact toughness damage at high temperature, and strong resistance to organic chemical corrosion such as corrosion resistance. And the size is wear-resistant and corrosion-resistant. It is widely used in wet ball mill lining, textile ceramics, argon arc welding machine nozzle, radio and electronic components, etc.
Both alumina ceramics and zirconia ceramics are one of the more popular products. The alumina ceramic is a structural ceramic with aluminum oxide (Al2O3) as the main body, used for thick film integrated circuit chips. Alumina ceramics have good conductivity, impact toughness and heat resistance. Zirconia ceramics are milky white, yellow or gray when they contain impurities, and generally contain HfO2, which is not easy to separate. There are three crystal states of pure ZrO2 under normal pressure.
The application of alumina ceramics in the current social development has already exceeded people's imagination. Not only people's usual applications are considered, but also various unique regulations can be considered.
Because of its good electrical properties, alumina ceramics are the most widely used in electrical and electronic applications. As a substrate material for electronic and electrical appliances, the surface metallization must be involved. Because ceramics are insulating materials, only the surface is metallized. To be electrically conductive.
Alumina ceramics are divided into two types: high purity type and ordinary type.
High-purity alumina ceramics refer to ceramic materials with an Al2O3 content of more than 99.9%. Because the sintering temperature is as high as 1650-1990 ℃, and the transmission wavelength is 1 to 6 μm, it is generally made of molten glass to replace platinum crucibles; It can be used as a sodium lamp tube for light and alkali metal corrosion resistance; it can be used as an integrated circuit substrate and high-frequency insulating material in the electronics industry.
Ordinary alumina ceramics are divided into 99 porcelain, 95 porcelain, 90 porcelain, 85 porcelain and other varieties according to different Al2O3 content. Sometimes those with Al2O3 content of 80% or 75% are also classified as ordinary alumina ceramic series. Among them, 99 alumina porcelain materials are used to make high temperature crucibles, refractory furnace tubes and special wear-resistant materials, such as ceramic bearings, ceramic seals and water valve discs; 95 alumina porcelain is mainly used as corrosion-resistant and wear-resistant parts; 85 porcelain Because it is often mixed with some talc, the electrical properties and mechanical strength are improved, and it can be sealed with metals such as molybdenum, niobium, and tantalum, and some are used as electric vacuum devices.
Because of its good electrical properties, alumina ceramics are the most widely used in electrical and electronic applications. As a substrate material for electronic and electrical appliances, the metalization of the surface must be involved. Because ceramics are insulating materials, only the surface is metalized. To be electrically conductive. What I want to tell you today is the surface metallization process of alumina ceramics.
Ceramic metallization is to firmly adhere a metal film on the ceramic surface to realize the welding between ceramic and metal. A more advanced application is to form a circuit on the ceramic surface, which can not only be welded, but also can be used as a wire to transmit current. At present, the traditional metallization methods include thick film method, DBC method, DPC method, LTCC, HTCC and Stone LAM.
The advantages and disadvantages of these processes are explained below one by one:
Thick film method
By screen printing, various circuits, resistors and capacitors are printed on the ceramic substrate. It is undeniable that this process is widely used and can carry larger currents. Most of the ceramic applications are realized by the thick film method, but Can it really cure all diseases? Everyone knows that the accuracy of screen printing is very unsatisfactory. The combination of silver paste and ceramics is not satisfactory. At the same time, the silver paste needs to be sintered at a certain temperature to be solidified. I believe there are several shortcomings. Many people in the industry have also been deeply troubled. Moreover, the thick film method has thicker circuits, which is a big obstacle to the miniaturization of electronic products. Therefore, everyone has to think of other methods.
This process is often applied to high-power modules. The copper layer is thicker, which can load larger currents, has good thermal conductivity, high strength, and strong insulation. The thermal expansion coefficient is matched with semiconductor materials such as Si. However, the ceramic substrate has low reactivity with metal materials and poor wettability. It is difficult to implement metallization. It is not easy to solve the problem of micro-pores between Al2O3 and the copper plate. In addition, the higher sintering temperature and the high cost can only be applied to Areas with special needs.
It is widely used in the LED field, and the technology is mainly in the hands of Taiwanese manufacturers. Tongxin Electronics accounts for more than half of its annual shipments. In addition, there is also Aspare. The biggest advantage of this process is high circuit precision, smooth surface, and comparison. It is suitable for flip chip/eutectic packaging. International LED manufacturers Cree and Osram are using Tongxin's substrates. The cost is lower than the DBC method, and the domestic DPC technology of Stone has been officially mass-produced.
Because LTCC （low temperature co-fired ceramic）uses thick film printing technology to complete the circuit production, the circuit surface is rough and the alignment is not accurate. Moreover, the multilayer ceramic laminate sintering process has the problem of shrinkage ratio, which limits its process resolution, and the promotion and application of LTCC ceramic substrates are greatly challenged.
Due to the high sintering temperature, this process has very few users and is basically replaced by LTCC（high temperature co-fired ceramic）.