1. Material technology (preparation of ceramic powder)
At present, the ceramic powder used for MLCC is mainly divided into three categories (Y5V, X7R and COG). Among them, X7R material is one of the most competitive specifications in the world, as well as one of the varieties with the largest market demand and electronic machine consumption. Its manufacturing principle is based on the modification of BaTiO3 nanoscale ceramic material. According to the demand of large capacity (more than 10μF), Japanese manufacturers (such as muRata) add rare earth metal oxide modification on the basis of wet BaTiO3 with D50 of 100 nm to produce X7R ceramic powder with high reliability, and finally make 10μF-100μF small size (such as 0402, 0201, etc.)MLCC. Domestic manufacturers add rare earth metal oxides to make X7R ceramic powder based on BaTiO3 with D50 of 300-500 nanometers. There is still a gap with foreign advanced powder technology.
2. laminated printing technology (laminated printing of multi-layer medium film)
How to manufacture MLCC with higher capacitance based on small size such as 0805, 0603 and 0402 has always been one of the important topics in MLCC industry. In recent years, with the continuous improvement of materials, technology and equipment level, The Japanese company has been stacking 1000 layers of 2μm thin film medium practice, the production of a single layer of 1μm thickness of 100μFMLCC, it has lower ESR value than chip tantalum capacitor, wider operating temperature (-55℃-125℃). On behalf of the domestic MLCC production of the highest level of Fenghua High-tech company can complete flow into 3μm thick film medium, burning into porcelain after 2μm thick medium MLCC, and foreign advanced laminated printing technology there is a certain gap. Of course, in addition to the powder that can be used for laminated printing of multilayer dielectric film, the degree of automation and accuracy of the equipment still need to be improved.
3. Co-firing technology (co-firing of ceramic powder and metal electrode)
MLCC element structure is simple, consisting of three metal layers of ceramic medium, inner electrode metal layer and outer electrode metal layer. MLCC is made of multi-layer ceramic medium printing electrode paste, superposition and co-firing. Therefore, it is inevitable to solve the problem of how to avoid delamination and cracking of ceramic medium and inner electrode metal with different shrinkage rates after firing at high temperature, that is, the co-firing of ceramic powder and metal electrode. Co-firing technology is the key technology to solve this problem. A good command of co-firing technology can produce MLCC with thinner medium (less than 2μm) and higher number of layers (more than 1000 layers). At present, The Japanese company in MLCC sintering special equipment technology leading other countries, not only have all kinds of nitrogen atmosphere kiln (bell jar furnace and tunnel furnace), but also in equipment automation, precision has obvious advantages.
Advantages of MLCC:
1. due to the use of multi-layer medium superimposed structure, high frequency inductance is very low, has a very low equivalent series resistance, so can be used in high frequency and VHF circuit filter without rival;
2. no polarity, can be used in the presence of very high ripple circuit or AC circuit;
3. use in low impedance circuit does not need to significantly derating;
4. no combustion explosion when breakdown, high safety.
