Development of aerosoljet printed miniaturized 3D coils for high speed power converters.
Begeleider 1: Herbert
Trefwoorden: coil, inductance, aerosoljet printing, integration, plastic, micro-injection moulding
Switched mode power converters (SMPS) do not escape from scaling, especially with the current trend towards wearable electronics. This means that these power converters have to be as small and light as possible. One very profiting evolution that helps to scale down the SMPS is the fact that the power switches (power MOSFETS e.g.) become faster and faster. With this positive driving force, the global switching frequency of the SMPS can be increased and the critical passive components to be scaled down.
the essential coils in an SMPS, this tendency towards high speed implies that
the required inductance can be lowered as well as the coil’s current rating.
Although these somewhat relaxed requirements, it is still a challenge to
fabricate high-Q coils that behave properly up to e.g. 10MHz.
In classic coil fabrication a copper wire is wound around a magnetic core. But as the required level of inductances tend to go down, the coil’s diameter gets very small and physical handling and wiring becomes a problem. By introducing the aerojet principle, the so-called microcoils can be created by an entirely new fabrication process and overcome the issues popping-up in the classical approach.
Figure 1: left: wire based microcoils; right: planar microcoil
Figure 2: Schematic of an aerosoljet-printed coil (gold spiral) around a polymer (blue) coated metal wire core, assembled on a printed circuit board with contact areas for both the core and the spiral coil.
Figure 3: First trial aerosol printed Ag-ink trace
Goals of the thesis
The thesis student will first simulate the behavior of the coils based on material properties of the metal core, the isolator and the aerosoljet printed metal inks and will derive a set of requirements for the shape, uniformity, thickness and geometry of the printed spiral tracks.
Afterwards, the candidate will develop an aerosoljet printing process for the realization of microcoils on a cylindrical carrier. In order to accomplish such a shape, the cylindrical carrrier needs to be rotated while the aerosoljet printer is translating. A basic set-up will be built by the thesis student to perform these movements in parallel. The obtained lines on the cylinder will be investigated and optimized by tuning the aerosoljet process parameters. Based on the optimal track fabrication parameters, protoype coils will be characterized. When the cylindrical carrier is replaced by a polymer coated metal wire, one can obtain a microcoil with integrated metal core; both situations can be investigated and compared.
Apart from the coil fabrication, an assembly approach will be developed for the obtained microcoils. The assembly scheme of the coils should be as such that the 3D metal contact lay-out of the coils plus the core can be translated to a 2D PCB-like interconnection scheme like shown in the schematic figure. This assembly approach allows the coil’s electrical characterization in a more reliable way and allows the interconnection of high speed signal connectors.
Locatie: Ardoyen (clean rooms) and from home.