What are the advantages and methods of fabricating metallized ceramic substrates?


As a typical inorganic non-metal material, ceramics seem to be in a completely opposite position to metals. Due to their outstanding advantages, people began to think about combining ceramics and metals, and thus ceramic substrate plating technology was born. .

Advantages of ceramic substrates:

1. Low dielectric loss - dielectric constant;

2. High thermal conductivity;

3. Thermal expansion coefficient, thermal expansion coefficient of ceramics and metals is close;

4. High adhesive strength, high adhesive strength between metal layer and ceramic;

5.The working temperature is high.Ceramic can withstand high and low temperature cycles with large fluctuations, and can even work normally at high temperatures of 500-600 degrees;

6. High electrical isolation. The ceramic material itself is an insulating material capable of withstanding high breakdown voltage;

When ceramics are used in circuits, it is first necessary to carry out a plating treatment, that is, a layer of metal film is applied to the surface of the ceramic, firmly bonded to the ceramic, but not easily melted, to make it conductive, and then welded to the metal to connect leads or other metal conductive layers rise up and become one. It can be said that the quality of the ceramic plating effect will directly affect the final packaging effect.

Commonly used ceramic substrate plating preparation methods mainly include Mo-Mn method, activated Mo-Mn method, active metal soldering method, direct copper plating (DBC) method and magnetron sputtering method.

1. Mo-Mn Method

The Mo-Mn method is based on the use of Mo raw material refractory metal powder, and then a small amount of low melting point Mn is added to the plating formula, a binder is added to wrap the surface of alumina ceramics, and then sintered to form a plating layer. The disadvantages of the traditional Mo-Mn method are the high sintering temperature, high energy consumption and the absence of an activator in the formulation, which leads to low sealing strength.

2. Mo-Mn Method Activation

The activated Mo-Mn method is an improvement on the traditional Mo-Mn method. The main areas of improvement are the addition of activators and the replacement of metal powders with oxides or salts of aluminum and manganese. The aim of the two improved methods is to lower the plating temperature. The disadvantage of the activated Mo-Mn method is that the process is complex and high in cost, but a reliable combination of the two can significantly improve wettability. As such, it is still the earliest invented process in the ceramic and metal densification process and has a wide range of applications.

3. Active metal soldering method

The active metal soldering method is also a widely used cermet sealing process that was developed 10 years later than the Mo-Mn method. It is characterized by fewer processes, and only one heating process is required to completely seal the ceramic with the metal. Solders contain active elements such as Ti, Zr, Hf and Ta. The added active elements react with alumina, forming a reaction layer with metallic properties at the interface. This method can be easily adapted for high volume production. Compared with the manganese method, this method is simpler and more economical.

The disadvantage of the method of active soldering of metals is that the active solder is single, which limits its application and is not suitable for continuous production. Only suitable for mass production, single or small batch production.

4. Direct copper plating DBC

DBC is a plating method in which copper foil is bonded to a ceramic surface, mainly aluminum oxide and aluminum nitride. This is a new technology developed with the advent of chip-on-board COB packaging technology. The basic principle is to introduce oxygen between Cu and ceramic, form Cu/O eutectic liquid phase at 1065-1083°C, and then react with ceramic substrate and copper foil to form CuAIO2 or Cu{AIO2}2, and then in the interphase Under the action, a combination of copper foil and substrate is realized.

5. Magnetron sputtering

Magnetron sputtering is a physical vapor deposition technique in which multilayer thin films are deposited onto a substrate using magnetron technology. Compared with other deposition methods, it has the advantages of better adhesion and less contamination. and also enhances the crystallinity of deposited samples to produce high quality films. The metallization layer obtained by this method is very thin, which makes it possible to ensure the dimensional accuracy of the part. The DPC process supports PTH (through hole), which can realize high-density assembly - line/space (L/S) resolution can reach 20um, and realize light weight, miniaturization and equipment integration.

As a new type of material, metallized ceramic substrate has many unique advantages, and metallized ceramic substrate materials will surely shine in the near future.