Enhancing microscale additive manufacturing: Electrolyte-column localized electrochemical deposition for microwire and microdevice substrate connection

Abstract

Electrochemical deposition is a microscale additive manufacturing technology. Due to the excellent performance of electrodeposited coating layers which exhibit no thermal stress, low porosity, and minimal microcracks, electrodeposition has been used in the connections of microdevices to solve the problems of shrinkage and deformation of microparts caused by thermal stress generated by conventional connections. Due to the low efficiency of Meniscus-Confined electrodeposition, a novel connection process for microwires and microdevice substrate using electrolyte-column localized electrochemical deposition (ECL-ECD) is proposed. The connecting mechanism is determined through simulation and experimentation. Simulation results indicated that the current density in the connection area exhibited a Gaussian distribution and the deposition layer preferentially grew at the interface between the microwire and the substrate. A high-speed camera was used to observe the liquid beam throughout the experiment, the results indicated that the microwires didn’t affect the stability of the liquid beam, and the ECL-ECD had excellent domain fixation. Smooth and dense surfaces on the connection area of the microwire and substrate were obtained at a current density of 50–60 A/dm2. Performance testing results showed that the connection point has excellent corrosion resistance and electrical properties. When the deposition time was short, the microwire was detached from the deposition area due to relatively thin deposition layer thickness and the tensile strength was only 133.82 MPa during the tensile testing. When the appropriate deposition process parameters were chosen, the fracture occurred on the microwire under tensile load and the fracture strength was 198.84 MPa, which equals the tensile strength of the microwire and indicated that the connection point can provide sufficient strength. The experimental results demonstrated that ECL-ECD can provide an effective and reliable connection process for the microwires interconnection.