Coreless transformers are an attractive technology for power electronics due to their light weight and the absence of a brittle magnetic core material.[1] A coreless transformer consists of a primary spiral inductor with few turns and a secondary spiral inductor with many turns stacked together. Aerosol jet printing (AJP) is an additive manufacturing technology which can be used to print metals and polymers with linewidths as narrow as 10 µm. In this work we have used a combined AJP, electroless deposition, and electrodeposition approach to fabricate multi-layer coreless flyback transformers. This combined approach makes accessible both the high-resolution patterning from AJP and the high-density, high-conductivity materials such as Cu and Ni from electrochemical deposition techniques.[2]

We have designed two-layer primary and secondary inductors separated by AJP-deposited UV-curable dielectric layers. Micrographs of the primary and secondary inductors are shown in Figure 1(a) and 1(b) respectively. Electroless deposition of Cu and electrodeposition of Cu and Ni are optimized in order to minimize resistive losses and promote uniform film growth. The typical inductances measured on the 2-layer primary are 0.2 µH and the inductances measured on single layers of the secondary are on the order of 4 µH. Initial testing of the transformer for flyback voltage conversion demonstrated the capability of generating an output to input voltage ratio of >50. Comparisons of the experimentally measured inductance of the primary and secondary inductors as well as the transformer voltage ratio will be compared with simulated models.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2021-15239 A

References:

[1] S.C. Tang, S.Y. Hui, H.S.-H. Chung. IEEE Transactions on Power Electronics. 15 (2000) 931–941.

[2] L. Tsui, S.C. Kayser, S.A. Strong, J.M. Lavin. ECS J. Solid State Sci. Technol. 10 (2021) 047001.

Figure 1. Additively manufactured coreless transformer showing (a) the two-layer Ag-Cu-Ni primary inductor spiral and (b) the addition of a dielectric separation layer and one secondary inductor layer.