Laser based metallization of materials with low wettability for joining of hybrid material combinations

In the field of high-performance components, different materials are increasingly being combined. The use of different materials allows an optimal local adjustment of the required component properties. Often, different materials such as ceramics (e.g. SiC, SiSiC, Si3N4, Al2O3, BN, WC, Zr02) and metals (e.g. Al, Cu, Ti) are combined. The bonding of such different materials, which are difficult to wet, is often carried out in a vacuum furnace using special active solders at temperatures of 850 °C and higher. However, heating the whole samples to such high temperatures often leads to high stresses and consequently to the formation of cracks both in the base material and in the coating. In addition, a furnace process is always associated with high energy costs and is a batch process, which means that it cannot be integrated into a production process chain.
This paper reports about a laser-based process for metallization materials that are difficult to wet. The aim is to achieve complete wetting of the surface, low-porosity and crack-free coatings, as well as sufficient adhesion of the coatings to the base material. The requirement for the subsequent soldering process is a minimum layer thickness of 20 µm. By using metallic micro or nano particles, the inks or slurries should be adapted to the laser process, especially the short temperature-time cycles. The metallization temperature can thus be reduced up to 50%. A reduction in the metallization temperature goes hand in hand with lower stresses in the components and thus a reduced risk of crack formation. Furthermore, in contrast to a furnace process, the laser-based metallization can be integrated in a process chain.
Applications can be found where material combinations are used, e.g. batteries, fuel cells, heat exchangers, LED or tools.