Alumina Ceramic Surface Metallization Process
Alumina ceramics are divided into two types: high-purity type and ordinary (calcined) type.
High-purity alumina ceramics refers to ceramic materials with Al2O3 content of more than 99.9%.
Because of its sintering temperature as high as 1650-1990 ° C and transmission wavelength of 1-6 μm, it is generally made of molten glass to replace platinum crucibles;
It can be used as a sodium lamp tube with light properties and alkali metal corrosion resistance; In the electronics industry, it can be used as an integrated circuit substrate and a high-frequency insulating material.
Ordinary (calcined) alumina ceramics are divided into 99 porcelain, 95 porcelain, 90 porcelain, 85 porcelain and other varieties according to the content of Al2O3, and sometimes those with Al2O3 content of 80% or 75% are also classified as ordinary alumina ceramics series.
Among them, 99 alumina ceramic 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 pieces;
95 alumina porcelain is mainly used as corrosion-resistant and wear-resistant parts; 8
5 Porcelain is often mixed with some talc, which improves the electrical properties and mechanical strength, and can be sealed with metals such as molybdenum, niobium, and tantalum, and some are used as electrical vacuum devices.
Alumina Ceramic Surface Metallization Process:
1. Thick film method
Various circuits, resistors and capacitors are printed on the ceramic substrate by screen printing.
It is undeniable that this process is widely used and can carry large currents. Most of the applications of ceramics are realized by the thick film method.
As we all know, the fineness of screen printing is not enough, and the combination of silver paste and ceramics cannot reach a satisfactory level. At the same time, the silver paste needs to be sintered at a certain temperature to be solidified.
2. DBC method
This process is often used in high-power modules. The copper layer is thicker and can carry larger currents. It has good thermal conductivity, high strength, and strong insulation. The thermal expansion coefficient matches that of semiconductor materials such as Si.
However, the reactivity of ceramic substrates and metal materials is low, and the wettability is poor. It is difficult to implement metallization, and it is difficult to solve the problem of micro pores between Al2O3 and copper plates. In addition, the high sintering temperature and high cost can only be applied to areas with special needs.
3. DPC method
It is widely used in the LED field, and the technology is mainly in the hands of Taiwanese manufacturers.
The biggest advantage of this process is that the circuit has high precision and smooth surface, which is more suitable for flip chip/eutectic packaging. Its cost is lower than the DBC method.
4. LTCC method
Due to the use of thick film printing technology to complete the circuit production of LTCC, the surface of the circuit is relatively rough and the alignment is not accurate.
Moreover, the multi-layer ceramic lamination and sintering process also has the problem of shrinkage ratio, which limits its process resolution and greatly challenges the promotion and application of LTCC ceramic substrates.
5. HTCC method
Due to the high sintering temperature, this process has very few users and is basically replaced by LTCC.
