Metallized ceramics

Your partner for metallized ceramics

Metallization for ceramics has two main components. It consists of glass (manganese disilicide) and metal particles (molybdenum (Mo) or tungsten (W)). The glass forms the bond to the ceramic, and the metal particles form the bond to the metal component via the solder. Alumina Systems produces its own metallization paste for this purpose. This is applied to the unglazed ceramic (layer thickness at least 5 µm) using a screen printing process, for example.

Metallized aluminum oxide ceramic

Depending on the shape of the surface to be metallized, other processes such as lining or brushing are also used. The metallization is then fired under a forming gas (90% nitrogen (N2) and 5% hydrogen (H2)). The forming gas protects the metal particles from oxidation during firing. This creates a bond between the metallization and the ceramic.

Nickel plating of the oxide ceramic metallized

To ensure sufficient wettability of the Al₂O₃ metallization by the solder, a thin nickel layer (0.5–5 μm) is applied electrolytically or chemically (electroless). All metallized ceramic components are nickel-plated to ensure wettability of the solder. Ceramic-metal assemblies are also frequently nickel-plated after soldering. Alumina Systems GmbH uses two methods for this in its in-house electroplating facility.

Chemical nickel metallization

This electroless nickel plating process produces uniform layer thicknesses with high levels of hardness, corrosion protection, and wear resistance. It is suitable for nickel plating complex-shaped components without electrical contact. Nickel plating is a coating of nickel (Ni) and phosphorus. Since the phosphorus can evaporate in a vacuum, this type of nickel plating is not recommended for vacuum technology. One advantage of incorporating phosphorus is the proven reduction of the ferromagnetic properties of the Ni layer. With specific pretreatment methods, aluminum alloys, ceramics, and glass can be coated in addition to steel and copper alloys.

Homogeneous layer thickness (5 µm to 50 µm)
Solderable
Matte to glossy surface appearance (depending on the initial surface)
Corrosion-resistant
Alkali-resistant

Galvanic nickel metallization

For the electrolytic nickel plating of pure nickel, the components must be electrically connected. Custom electroplating racks must be built for this. The layer is ferromagnetic. The properties of the nickel layer protect the metallic components against corrosion and wear. High-gloss coatings as well as matte surfaces can be produced using appropriate combinations.

Advantages of electroplating nickel:

Solderable
Corrosion-resistant
Decorative appearance

Gold plating metallized technical ceramics

For oxidation protection or to enable bonding with thin or thick aluminum wire, Alumina Systems can apply an additional thin gold layer using the ENIG (Electroless Nickel/Immersion Gold) process in its in-house electroplating facility. The metallized ceramic can be joined using either brazing or soft soldering.

With ENIG (Electroless Nickel/Immersion Gold) gold plating, only a thin layer of 100 nm to 200 nm can be deposited. This serves to protect the underlying nickel layer against oxidation and ensures excellent solderability and ultrasonic bondability with aluminum wire. Alumina Systems can apply this gold layer to previously nickel-plated components using an exchange reaction in its own electroplating facility.