For capacitors, miniaturization and high capacity are eternal trends. Among them, the number of multilayer ceramic capacitors (MLCC) is the fastest growing.
Multi-layer ceramic capacitors are widely used in portable products, but in recent years, technological advances in digital products have placed new demands on them. For example, mobile phones require higher transmission rates and higher performance; baseband processors require high speed and low voltage; LCD modules require low thickness (0.5mm) and large capacitance. The harshness of the automotive environment has special requirements for multilayer ceramic capacitors: first, high temperature resistance, multilayer ceramic capacitors placed in it must meet the operating temperature of 150 ° C; secondly, short circuit failure protection design is required on the battery circuit. .
That is to say, miniaturization, high speed and high performance, high temperature resistance and high reliability have become key characteristics of ceramic capacitors.
The capacity of the ceramic capacitor varies with the DC bias voltage. The DC bias voltage reduces the dielectric constant, so it is necessary to reduce the dependence of the dielectric constant on the voltage from the material side and optimize the DC bias voltage characteristics.
The most common application is X7R (X5R) multilayer ceramic capacitors, whose capacity is mainly concentrated above 1000pF. The main performance index of this type of capacitor is equivalent series resistance (ESR), decoupling and filtering of power supply with high ripple current. The low-power performance of the low-frequency signal coupling circuit is outstanding.
Another type of multilayer ceramic capacitor is C0G, which has a capacity of less than 1000pF. The main performance index of this type of capacitor is the loss tangent tgδ(DF). The traditional noble metal electrode (NME) has a DF value range of (2.0 to 8.0) × 10-4, while the technically innovative base metal electrode (BME) has a DF value of (1.0 to 2.5) × 10-4. , about 31 to 50% of the former. These products have significant low-power characteristics in GSM, CDMA, cordless phones, Bluetooth, and GPS systems with T/R module circuits. It is mostly used in various high frequency circuits such as oscillation/synchronizers and timer circuits.
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