Patent DE-10021490-A1 (DE)
Title: Micro fabrication of geometric three-dimensional micro structures forms a laminate of a hydrophilic polymer and a hydrophobic resin with structured recesses for electroplating and final separation
Inventor: LIN CHING-BIN
IPC: C25D1/00
Filed: 2000-05-03
Abstract: The micro production process, to give geometric miniaturized micro structures (5), applies a swelling action to at least one hydrophilic polymer (1) to shrink the dimensions of each recess (H) on a micro-processed micro structure of assembled three-dimensional entities. Each recess is filled with metal by plating or deposition. In the micro production process, an electrolyte solution is prepared for use in plating. A hydrophilic polymer, which can absorb an electrolyte solvent, is applied to a hard hydrophobic resin (2) which does not absorb the electrolyte solvent to form a laminated unit structure. A number of laminated units are assembled together in a packet of alternating layers. A thin electrically insulating mask (3) is applied to all the outer surfaces. A number of recesses are formed to give a three-dimensional micro structure and an inner contact with a plate cathode (4).  The bonded laminated structure is immersed in the electrolyte for electro shaping, where the solvent transfer of the electrolyte solvent into the polymer swells the laminate to shrink the dimensions of each recess in the polymer. The electro plating fills each recess with metal and alloy in the saturated laminated structure. The desorption from the swollen polymer is through heating the electrolyte, to shrink it and recover the polymer, to separate a multi-layer micro-structured product from the laminated material, with a high aspect ratio.  The polymer can be applied to the surface of a resin which has not fully hardened, for bonding between them by interchange of their molecular chains at the butting surfaces. An electrically insulating film is applied to the outer surfaces of the laminated structure with the polymer layers in a sandwich between the resin layers, for immersion in the electrolyte bath for plating.  The process has a further stage for the production of a venturi tube with a throttle section, using a micro-structured produce with a narrow throat section and two expanded sections flanking it. In an alternative production process, a cube of hydrophilic polymer is coated on six sides with a thin electrically insulating layer. A number of recesses are drilled into three surfaces to intersect the X-, Y- and Z-axes at right angles, parallel to the axes. Three recesses from the three surfaces intersect in at least one common point at right angles to the corresponding location of the coordinates of the three flat surfaces.  The three surfaces are fitted with plate cathodes, and the body is immersed in electrolyte, which diffuses into the polymer through the recesses. The swollen polymer is electroplated with a metal deposit. The plated micro structure is separated by heat to give a three-dimensional micro-structured product.  The separation is through immersion in hot water to release the polymer and leave a three-dimensional metal grid. In a further variant, the hydrophilic polymer is laid on a hot metal plate to give it up to a 95% cross linking, to be covered by a further metal plate to form a sandwich. This is repeated to form a multi-layer structure, and the outer surfaces are covered with a thin and electrically insulating masking film. The structure is given a micro working to form a number of recesses vertically through the laminations. The lamination is bonded internally, and the structure is immersed in an electrolyte for it to diffuse through the polymer for swelling and electroplating.  The layers are separated in hot water. The structure can also be formed by a number of overlaid polymer layers in a series of varying molecular weights from top to bottom, to give a lamination of different hydrophilic polymers. The outer surfaces are covered with a thin electrically insulating film, and recesses are formed.  During immersion in the electrolyte, the polymers with the lower molecular weights swell more than the other polymers. The structure is electroplated, and then the layers are separated to give a micro structure in layers where the diameters change in steps.