Novel Fabrication Method of Microcoil Springs Using Laser-Scan Helical Patterning and Nickel Electroplating

Abstract

A novel microcoil fabrication method was developed. In the past research, copper microcoils were fabricated by wet-etching copper pipes with helical resist patterns formed using laser-scan lithography. However, etched coil widths often locally fluctuated owing to the influence of the surface and backsurface conditions of the pipes, and it was difficult to consistently fabricate microcoils with homogeneous widths. For this reason, in the new method, microcoils are fabricated by nickel electroplating instead of etching. After forming helical patterns on a fine stainless-steel wire with a diameter of 80 µm, nickel was electroplated in the spaces of resist patterns. Because the adhesion of nickel to the stainless-steel wire was not very strong, helically electroplated nickel was tore off from the core wire, and the microcoil was fabricated when the wire was pulled and lengthened. Next, helical pattern widths and nickel coil widths were evaluated. The homogeneity and reproducibility of both widths were very good, and width variations of nickel microcoils were almost the same level as those of resist space patterns. This finding was considered to indicate that the width fluctuation occurring during the electroplating process was very small. The fabricated nickel coils showed almost linear spring characteristics when they were repeatedly compressed and released. The spring constant of the fabricated coil was approximately 0.16 N/mm. The new method and the fabricated nickel coils will be of practical use.

Laser-Scan Lithography and Electrolytic Etching for Fabricating Meshed Pipes of Stainless Steel

“…Recently, various micro-components with three-dimensional (3D) cylindrical shapes are required. They are used as contact-probe springs in testing systems of semiconductor integrated circuits [1], syringe needles with surface textures for detecting their positions when they are stuck into bodies [2], medical stents [3][4][5], surgery tools [6], micro-needles [7] and others [8][9][10][11][12][13][14][15].…”

Guided Formation of 3D Helical Mesostructures by Mechanical Buckling: Analytical Modeling and Experimental Validation

“…3D helical mesostructures hold great potential for a broad range of applications in microsystem technologies, such as microelectromechanical systems (MEMS), electrodes for lab‐on‐a‐chip systems, and stretchable electronics . To form 3D architectures of helical and other relevant topologies at the micro/nanoscale, several classes of fabrication/assembly approaches have been developed by exploiting different working mechanisms . Representative approaches include microcontact printing, MEMS lithography/electroplating techniques, manual winding, residual‐stress‐induced self‐rolling of thin films/belts, controlled mechanical buckling, and 3D additive printing based on direct ink deposition, or direct laser writing (sometimes in combination with liquid metal paste filling or the electrochemical deposition and plasma etching) .…”

“…To form 3D architectures of helical and other relevant topologies at the micro/nanoscale, several classes of fabrication/assembly approaches have been developed by exploiting different working mechanisms . Representative approaches include microcontact printing, MEMS lithography/electroplating techniques, manual winding, residual‐stress‐induced self‐rolling of thin films/belts, controlled mechanical buckling, and 3D additive printing based on direct ink deposition, or direct laser writing (sometimes in combination with liquid metal paste filling or the electrochemical deposition and plasma etching) . Most of these approaches, such as lithography/electroplating techniques, manual winding, and 3D additive printing, apply directly only to certain classes of materials, e.g., metals and/or polymers, and generally not to high‐performance semiconductors (e.g., single‐crystal silicon) or other advanced materials that are widely adopted in modern high‐quality electronics and optoelectronics.…”

“…Representative approaches include microcontact printing, MEMS lithography/electroplating techniques, manual winding, residual‐stress‐induced self‐rolling of thin films/belts, controlled mechanical buckling, and 3D additive printing based on direct ink deposition, or direct laser writing (sometimes in combination with liquid metal paste filling or the electrochemical deposition and plasma etching) . Most of these approaches, such as lithography/electroplating techniques, manual winding, and 3D additive printing, apply directly only to certain classes of materials, e.g., metals and/or polymers, and generally not to high‐performance semiconductors (e.g., single‐crystal silicon) or other advanced materials that are widely adopted in modern high‐quality electronics and optoelectronics. Although the methods based on residual‐stress‐induced self‐rolling are naturally compatible with modern planar technologies and offer yields and throughputs necessary for practical applications, they provide direct access only to certain classes of hollow polyhedral or cylindrical geometries, with the upper length scales limited, to a certain extent, by the achievable levels of residual stresses.…”

Fabrication of Stainless‐Steel Microcoils and Mesh Pipes Using Lithography

“…With such technologies, space between resist patterns is filled by metal through plating or sputtering. The authors formed helical patterns on stainless steel (SUS 304) wire, plated nickel in the spacing, and then removed the stainless wire core to produce a nickel microcoil . However, it takes a long time to obtain a thick film by plating or sputtering, and it is difficult to ensure thickness uniformity and reproducibility.…”