Thickness nonuniformity is one of the prominent problems in the electroforming process of the metal microfluidic chip mold, which decreases the dimensional accuracy of the mold, and has a direct influence on the usability of the microfluidic chip. A novel method of auxiliary cathode for improving the thickness uniformity of electroformed mold is presented in this paper. Compared with the traditional method of the auxiliary cathode, a coplanar auxiliary cathode similar to the local microstructure of mold is used to fabricate the electroformed mold, and the thickness uniformity of electroformed mold is improved obviously. In addition, in order to determine the dimensions and placement of the auxiliary cathode, the computer-aided analysis is performed to simulate electroforming process. The simulated results show that with the help of a specially designed auxiliary cathode, the thickness uniformity is improved by about 53.2% compared with the result without the auxiliary cathode. Finally, based on the simulation, a microfluidic chip mold is fabricated by micro electroforming with the coplanar auxiliary cathode. The result shows that the thickness uniformity of the mold is improved by about 49.1%, which is in good agreement with the simulation result.

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In order to reduce the large residual stress in micro elelctroforming layer, megasonic assisted electroforming is proposed here. Micro electroforming experiments were performed with and without megasonic agitation, respectively. Four different megasonic power densities were applied to investigate the influence of megasonic agitation on reducing the residual stress. The residual stress was measured by X-ray diffraction (XRD) method. Experiment results show that the residual stresses fabricated with megasonic agitation are less than that fabricated without megasonic. When the megasonic power density is 2 W/cm, the residual stress can be the minimum value of -125.7 MPa, reduced by 60% in comparison with the value of -315.1 MPa electroformed without megasonic agitation. For exploring the mechanism of megasonic agitation on reducing the residual stress, the dislocation density and crystal orientation were calculated by the single-line Voigt profile analysis and Relative Texture Coefficient (RTC) method, respectively. The diameters and distributions of pits on the surface of electroforming layer were observed by the STM-6 tool microscope and counted by the Image-Pro Plus software. It reveals that one hand of the mechanism is the acoustic streaming produced by megasonic can strengthen the motion of dislocation in crystal lattice and makes the crystal lattices grow towards the equilibrium shape, which is benefit to crystallization with low residual stress. When the megasonic power density is 2 W/cm, the dislocation density increases to be the maximum value of 8.09 × 10 m and the difference between RTC and RTC decreases to be zero, which is consistent with the residual stress results. The other hand is that the stable cavitation produced by megasonic can provide residual stress release points during the electroforming process.