Fabrication of Custom Printed 3D Air Core Inductors
There have been many circuit design advancements for power electronics in recent years that have allowed the creation of higher switching frequency circuits. Though experimental testing of these high frequency circuits has indicated numerous benefits, including circuit miniaturization while still maintaining high efficiency operation, there is a need for creating low loss magnetic devices to keep up with this advancing design strategy. The size allowance for inductors is very small for these circuits. One possible answer to this issue is the use of air core inductors designed with toroidal shapes to be used in these high frequency power conversion applications. Air core inductors are viable because the inductance needed is low. Furthermore, these inductors have lower cost and weight compared to inductors made from magnetic materials. Additionally, toroidal shapes have the benefit of containing the electromagnetic field. Currently, there is no feasible fabrication method that can create such an inductor. This research project is investigating methods to feasibly fabricate such inductors through the use of 3D printing and electroplating techniques. Developed models for these inductors will enable extensive comparison with commercial inductor designs for similar applications.
A prototype air core toroidal inductor electroplated with copper
The goal of this research is to realize the feasibility of fabricating 3D printed inductors and optimize them for power electronic circuits mentioned in the application section. To first prove these components can be feasibly fabricated, air core inductor prototypes with a range of toroidal geometries are designed using 3D design software such as Autodesk Inventor. Once created, the models are printed using a 3D printer with SLA plastic material. These designs will be used to test possible fabrication methods.
The current fabrication method under examination utilizes the chemical process of electroplating. This process uses electrical current passing through an electrolytic solution (copper sulfate) to move dissolved copper ions from an anode of pure copper to a cathode, the 3D printed inductor, which will coat it with a layer copper. These plated copper layers have been experimentally observed to be on the order of 10-100 micrometers thick. To allow the cathode to conduct current, the 3D printed inductor must first be coated with conductive paint. Different types of paint have been tested in this research, but the current method that obtains the best results utilizes a pre-coating layer of Caswell Copper Conductive Paint and an outer painting layer of MG Chemicals Nickel Ink. Once the electroplating process deposits a thin layer of copper on the outer surface of the inductor, the inductor is analyzed to determine the success of the plating experiments. Once the process yields a result that is deemed sufficient, the inductor's electrical properties are further analyzed. The inductance and AC/DC resistance is observed across a broad range of frequencies, and these measurements are compared with various commercial products to better understand how the custom inductor performs and which applications it is best-suited. Further evaluation of these inductors are done through 3D simulators such as Maxwell ANSYS to observe the inductor's predicted characteristics. The goal is then to further optimize the size and shape of the inductor to achieve maximum operational efficiency for circuit applications.
How WBG Can Help
Wide band gap (WBG) devices are allowing faster switching frequencies and more power efficient operations. Due to the success of these WBG technologies, these devices are no longer the largest source of loss in many high frequency electronics. To maximize the potential of WBG applications, this project is researching the improvement of efficiency in magnetic components by reducing conduction losses due to DC/AC resistance, containing the electromagnetic field from interring with other circuit components, and allowing circuits to continue to be miniaturized. The project proposes a 3D printed air core inductor with a toroidal shape as a possible solution. Future WBG applications would benefit from improved such a magnetic component to enable further advancement.
- Quillen Blalock