Single layer capacitor (SLC) is becoming more and more popular in order to adapt to the trend of miniaturization, integration and high frequency of electronic components. The structure of single layer capacitor consists of single ceramic dielectric layer and upper electrode layer and lower electrode layer respectively located on opposite surface of ceramic dielectric layer. Compared with multi-layer capacitor, single layer capacitor has a longer current path, lower equivalent series resistance and equivalent series inductance under RF and microwave conditions, thus have a higher self-resonant frequency and quality factor.
However, the thickness of single layer capacitor is thin, the existing sintering process is prone to deformation, which affects the smoothness and performance of the finished product. The existing process of processing electrode layer is usually thick film printed circuit, which is difficult to achieve ultra-thin thickness of the processed electrode layer, which is not favorable to realize the miniaturization of single layer capacitor, and the loss of electrode material is large. The chip capacitor is easily broken by the general mechanical cutting method and the rate of finished products is low. In order to solve the above problems, EXSENSE Electronics Technology Co., Ltd. introduces a kind of single layer capacitor, which has excellent performance and high rate of finished products.
The preparation method of this single layer capacitor include ceramic paste preparation, ceramic substrate preparation, sintering, cleaning, electrode layer attaching, dicing. Among them, the sintering curve is composed of heating adhesive discharging section, rapid heating section, high temperature section, heat preservation section and cooling section. The temperature range from room temperature to 400℃ is the heating adhesive discharging section, the heating rate is controlled at 0.8~1.5℃/min; 400℃ to 1000℃ is the rapid heating stage, the heating rate is controlled at 3.5~5 ℃/min; The temperature range from 1000℃ to the highest is high temperature, the heating rate is controlled at 2~3 ℃/min; When the temperature reaches the highest sintering temperature, it enters the heat preservation section, the highest sintering temperature is 1250~1320℃, and the heat preservation time is 2~3 hours; The cooling rate in the cooling section is controlled at 4~5 ℃/min. Single or multi-layer metal electrode layer is attached on the upper and lower surface of ceramic dielectric layer by vacuum sputtering process; During vacuum sputtering, the vacuum degree is controlled at 5×10-3×10-3Pa, the temperature is controlled at room temperature to 60℃, the target sputtering current is controlled at 1A-5A. Cutting using laser cutting, the cutting rate of laser cutting is 100mm~200mm/s, the power is 5~12W, the repeated cutting times is 1~4 times.
This single layer capacitor is thin thickness, small size, and has ultra-low series equivalent resistance and series equivalent inductance, which can be used in hybrid microwave integrated circuits, single-chip microwave integrated circuits, etc. The electrode layer of the single layer capacitor are processed by vacuum sputtering process to ensure good contact between the electrode layers, so that the product has ultra-low ESR value, which can significantly improve the effective gain of microwave circuit and reduce insertion loss. The electrode layer obtained by vacuum sputtering process is very thin, which can increase the thickness of the product almost negligible. It can meet the requirements of miniaturization of single layer capacitor and save the electrode material. By using laser cutting method to dice chip capacitor, cutting step can be set according to the required peripheral size, which is high precision and the chip capacitor is not easy to break, effectively solve the problem of general mechanical cutting method easy to damage the chip capacitor.