A. Steinmark, I. Ivanov, A. Peters
Keywords: ceramics, aluminum nitride, powered electronics, non-oxide ceramics
Summary:Power electronics are currently used in nearly all forms of modern transportation. Standard packaging for these modules are limited in terms of materials and producible geometry using conventional manufacturing methods. The capability to additively manufacture this packaging introduces the ability to design more complex, efficient, and lighter power electronics assemblies. Synteris is developing a novel AM process for the creation of non-oxide ceramic parts, most notably aluminum nitride and silicon carbide. By integrating this packaging into electric vehicles, it will allow them to access new terrain and travel further distances. Aluminum nitride ceramics can vastly increase the electrical efficiency in power devices by managing the energy lost as heat. This is particularly important for electric vehicle manufacturers as the industry moves towards “Zero Emissions” transportation. Conventional manufacturing methods for aluminum nitride are limited in terms of the geometry that is able to be produced. Using our Selective Laser Reaction Sintering (SLRS) technology, heat sinks and other cooling architectures can be fabricated with more complex geometry. Our manufacturing process uses minimal raw material allowing for rapid production of prototypes and can be used to reduce packaging volume and weight. The Selective Laser Reaction Sintering (SLRS) process is similar to the standard Direct Metal Laser Sintering (DMLS) or Selective Laser Melting (SLM) process used for metal additive parts, though instead of using an inert gas to expunge any oxygen and allow for increased bonding between particles, the chamber is filled with a reactive gas which the sintering laser breaks down and causes a reaction, forming the desired non-oxide ceramic. We use a proprietary mix of precursor powders to achieve near “net-shape” geometry during the SLRS process. This technique has also been proven for other materials such as SiC, TiC, TaC, and TaN as the process is materials agnostic for non-oxide ceramics. Most notably, this process does not include binders and as such requires no secondary debinding step. Preliminary experiments have been performed in a lab setup and also with a more advanced industrial-scale tool. Lab tests were performed by flowing the reactive gas through a quartz tube loaded with the precursor material, while a small laser converted and sintered the powder into the desired shape. Larger scale tests were performed on a Sintratec S2 SLS system which involved modifications to the system to incorporate the reactive gas flow, while still protecting sensitive areas of the machine that were not chemically compatible. Proof of concept studies were performed using this process and characterization was undertaken by way of optical, XRD, and SEM inspection. Synteris is continuing to scale up this process and is currently developing modifications for an SLM machine, a Renishaw AM400. These efforts are notably more complex than with previous experiments, as significant components in the machine need to be replaced to ensure chemical compatibility.