Toward Control of Microstructure in Microscale Additive Manufacturing of Copper Using Localized Electrodeposition

Abstract

The progress in microscale additive manufacturing (μ-AM) of metals requires engineering of the microstructure for various functional applications. In particular, achieving in situ control over the microstructure during 3D printing is critical to eliminate the need for post-processing and annealing. Recent reports have demonstrated the possibility of electrochemical μ-AM of nanotwinned metals, in which the presence of parallel arrays of twin boundaries (TBs) are known to enhance mechanical and electrical properties. For the first time, the authors report that the microstructure of metals printed using the microscale localized pulsed electrodeposition (L-PED) process can be controlled in situ during 3D-printing. In particular, the authors show that through electrochemical process parameters the density and the orientation of the TBs, as well as the grain size can be controlled. The results of the in situ SEM microcompression experiments on directly 3D-printed micro-pillars show that such control over microstructure directly correlates with the mechanical properties of the printed metal.

Metals by Micro‐Scale Additive Manufacturing: Comparison of Microstructure and Mechanical Properties

“…The normalized H data should be treated with corresponding care, although we tried to select a value that is most representative of the available literature. References for literature data: EHDP, [42] LAEPD, [43] LIFT (ink), [47,78,79] MCED, [26,51] FluidFM, [54] EHD-RP, [57] FEBID. [22,[59][60][61][62] *: Pt nanoparticles embedded in a carbonaceous matrix.…”

“…Electrochemical MCED -Meniscus-confined electrodeposition [16,26,[50][51][52] Cu 128 [51] 2 [51] 0.63 -0.962 [26,53] 114.2 -121.8 2.71 0.774 FluidFM -Confined electrodeposition in liquid [54][55][56] Cu 0.7 -0.9 [54] 134.0 -138.4 2.28 0.962 EHD-RP -Electrohydrodynamic redox printing [57] Cu 81 [57] 1 -1.5 [57] 80.4 -81.7 2.22 1.10 -1.38…”

“…In general, microstructural data comparable to our observations have been published earlier. [26,51,54,97,98] As a result of the high density, the measured elastic and plastic properties (E: 114 -138 GPa, H: 2.3 -2.7 GPa) can easily compete with properties of Cu films prepared by sputtering or electroplating (E: 130 GPa, H: 2 GPa for a grain size of 100 nm [72] ). The high materials quality of electrochemically 3D printed Cu is confirmed by previous studies of its mechanical [26,51,53,54] and electrical [16,98] properties.…”

A Hybrid Process for Printing Pure and High Conductivity Nanocrystalline Copper and Nickel on Flexible Polymeric Substrates

“…During printing in a confined area, electrodeposition can be slower than bulk (bath) electrodeposition due to several factors including smaller cathodic surface area, and the absence of electrolyte agitation. In the LED process, several factors can affect the printing process, including optimizing the electrolyte bath parameters such as the electrolyte pH and concentration, as well as the applied current density 27 . Increasing the cathode surface temperature or electrolyte temperature, by applying external heat source, may also improve the speed of the process.…”

“…Hence, overall the printed metal has columnar nanocrystalline texture. By changing the process parameters, it should be possible to control the microstructure of the printed metal to a great extent 27,34,35 .…”