Dr. Rudolf Eberle-prize 2004

Due to the increasing usage of power electronics on cooling- and carrier elements, better thermal conductivity characteristics of electronic parst are necessary. With the world-first suitable-for-series-production application of cold spraying, aluminium parts can be coated with copper in such a pure, oxide-free form that they can reach about 90% of the heat- and electrical conductivity of pure copper. Until now the soldering of aluminium and copper was complicated; the new coatings are solderable without problems and do not need a special pre-treatment.

It's also environmentally friendly. Cold sprayed coatings are, due to their dense structure, a real alternative to many technologies that are harmful to the environment; like the water contaminating electroplating or leaded solder for materials that are hard to solder otherwise. With the application of cold spraying it was possible to leave thermal spraying behind and turn towards kinetic spraying technology. The low heating-up of the materials enables coating for heat-sensitive surfaces.

Starting position

Russian scientist Anatoli Papyrin detected mid 80s, while doing particle supersonic flow experimentations, that at a certain velocity the electroerosion of the particles turned into a compact adhesion. That resulted in the development of cold spraying. Innovative technology was exclusively used by Technical Universities and research institutions for further development and application-technological tests, so far. The application technology, turning from thermal towards kinetic energy for sprayed coatings, was an unused novelty in practice. Its particular advantage , compared to previous thermal spraying technologies, is that the coating material is not melted or fused to the surface.

The high kinetic energy of the sprayed particles alone produces a dense coating or structure on the substrate. Nitrogen gas, fuelled with spraying materials in powder form, is accelerated ultrasonic in a de Laval nozzle and sprayed onto the substrate. The challenge is to use this revolutionary coating technology in practice, especially in ready-for-series-production applications, to produce affordable coatings.

Innovation

With intense and goal-oriented development- and research studies for the production of applicable and affordable coatings, it was possible for us to apply the advantages of cold sprayed coatings in practice and offer it to the market. During a nearly two year long development period with different spraying parameters and laboratory tests, we were able to achieve excellent coating characteristics on customers' prefabricated parts. In 2003 OBZ successfully put the first aluminium cooling element on the market, the first cold spraying coated series product ever. Hereby aluminium parts can be coated with copper in such a pure, oxide-free form that they can reach about 90% of the heat- and electrical conductivity that pure copper has. Up until know it was considered impossible for atmospheric spraying technologies to achieve more than 50% of the heat- and electrical conductivity that copper has. Not only are the new coatings easily solderable, they also do not need a sandblasting pre-treatment for the bonding. Those are ideal requirements for application in the electronics industry; for example coated aluminium cooling elements for computers, which show the huge advantage of cold sprayed copper coatings. Aluminium cooling elements prevent computer processors from over-heating, but high-performance processors produce more heat than aluminium heatsinks can dissipate. A highly heat conductive copper coating with a massive copperplate soldered on it solves this problem, but until now soldering copper and aluminium was problematic.

With an interlayer applied by cold spraying, different components are solderable without problem. This allows all the advantages of aluminium to be used, from the low weight to the simple and cost-effective processing, e.g. through impact- or profile extrusion. Due to the application of electrically and thermally conductive coatings on cooling elements and carrier components, ideal requirements for the electronic industry were created. The fact that this innovative technology can be applied to mass production of different prefabricated parts shows the innovative achievement of OBZ. Thanks to the professional application of cold spraying, new products and niche markets were rendered possible. A special in-house development of obz innovation gmbh deals with the manufacturing of inductive cookware, which is also coated via cold spraying. Cold sprayed coatings, e.g. from heavy metals as copper, nickel or zinc, can be used as alternatives to galvanically produced coatings from the same metals, due to their dense structure. The use of water polluting substances that is unavoidable for electroplating is thereby avoided or limited. Furthermore, cold spraying allows for the replacement of leaded solder with safer materials that can be easily soldered, thus making the application of unleaded solder possible . Exemplary would be copper, sprayed on the easy-to-solder prefabricated component.

Company

The still young company, founded in 1997 as OBZ Dresel & Grasme GmbH, is one of the most innovate companies in the area of thermal spraying. Since its founding its goal has been to achieve the highest quality in the application of the newest technologies while protecting the environment and mankind. With the application of the revolutionary cold spray coating technology, it was possible to use this process for industrial serial production as first job coater worldwide.

Several orders for new coating developments on customer's prefabricated parts, as well as serial orders, prove the commercial success of the applied technology. Therefore the number of employees has been increased from 10 to 15. A healthy willingness to take risks, invest in the most modern technologies, and develop their innovative application, is what makes the company successful.