Additive Manufacturing of Inductors and Transformers by Hybrid Aerosol Jet Printing and Electrochemical Deposition

Aerosol jet printing (AJP) is an attractive additive manufacturing process for printed electronic applications due to its high resolution (< 10 µm), flexible stand-off distance, and support of both metal and dielectric materials. A slow deposition rate (< 1 µm per layer) and the relatively low conductivity achievable with commercially available nanoparticle inks (~40% bulk) present some of the current limitations associated with AJP. Electrochemical deposition methods including both electrodeposition and electroless deposition are widely used in the microelectronics industry. Dense, high conductivity layers several 10s of µm can be deposited with well-established plating processes. Metals including Cu and Ni which are challenging to deposit by AJP, can be easily/readily deposited using commercially available plating baths. A hybrid approach of seed layer deposition using AJP and electrochemical deposition of highly conductive copper is used to improve the overall conductance of the printed structures. [1] Here, we apply this combined approach to the manufacturing of transformer and inductor devices. We have successfully prepared a two-layer secondary inductor on top of a two-layer primary inductor to form a coreless flyback transformer (Figure 1(a)). These inductors were fabricated by AJP of an Ag seed layer, followed by electroless deposition and electrodeposition of Cu and Ni. UV-curable dielectric polymer layers were deposited by AJP to separate each inductor layer. The flyback transformer produced a gain of 75.3x with an input voltage of 17 V at 400 kHz resulting in an output voltage of 1250 V (Figure 1(b)). We also demonstrated the repeated stacking of 8 coil layers by AJP of Ag seed layers and electrodeposition of Cu and Ni (Figure 1(c)). These inductors had an average equivalent series resistance of 0.6 Ω and a 1.7 µH inductance at 100 kHz (Figure 1(d)). Finally, we will study the deposition of these inductor and transformer devices on magnetic substrates, characterizing changes in inductance and gain. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2022-17001 A References: [1] L. Tsui, S.C. Kayser, S.A. Strong, J.M. Lavin. ECS J. Solid State Sci. Technol. 10 (2021) 047001. Figure 1 . (a) Additively manufactured coreless flyback transformer fabricated by combined aerosol jet printing, electroless deposition, and electrodeposition. (b) Output voltage vs. input voltage at 400 kHz resulting in a gain of 73.5x. (c) 8-layer inductor fabricated by combined aerosol jet printing and electrodeposition. (d) Inductance at 100 kHz as a function of number of layers for the multi-layer inductor up to 8 layers. Figure 1