Quantitative relationship between crystallite size and adhesion strength of the electroforming layer during microelectroforming process

Many micrometal devices are fabricated by microelectroforming technology in microelectromechanical systems. Micrometal devices usually suffer from poor interfacial adhesion strength, which restricts the application of microelectroforming technology. To solve this problem, in this reported work the influence of the electroforming crystallite size on practical adhesion energy is investigated. Furthermore, based on the energy balance criterion of fracture mechanics, the Miedema model of experimental electron theory (Miedema model) and the surface stress model, the equations between the crystallite size and the practical adhesion energy are established originally. Concerning the equations, the results show that the practical adhesion energy keeps an increasing trend and approaches basic adhesion energy as the crystallite size increases. To prove the equations, microelectroforming experiments were performed. The practical adhesion energy was measured by a scratch test. The crystallite size of the electroforming layer was tested by X-ray diffraction technology. The results of the experiments show that, within the range of the crystallite size, the practical adhesion energy keeps an increasing trend and approaches 15 J/m². The theoretical and the experimental results show the same trend. The equations are verified by the experiments and this work may guide the microelectroforming process.