Influence of electrodeposited crystallite size on interfacial adhesion strength of electroformed layers

Abstract

Microelectroforming is an important method for fabricating metal devices in microelectromechanical systems. However, the metal devices are limited by poor interfacial adhesion strength between the electroformed coating and the substrate. To improve the adhesion strength, the authors' research group presented a small current density deposition method. The purpose of this Letter is to investigate the mechanism of this method regarding the effect of the electrodeposited crystallite size. The mechanism is that a small current density can cause a big crystallite size which reduces the compressive stress. Therefore the adhesion strength is large under a small current density. To investigate this mechanism, different current densities were applied during the microelectroforming experiments. The crystallite size of the electroformed coating was measured by the X-ray diffraction method, and the adhesion strength was calculated by a scratch test. The experimental results indicate that within the range of the current density from 0.2 to 2 A/dm 2 , the crystallite size decreases from 30.1 to 23.7 nm and the adhesion strength decreases from 14.89 to 8.12 J/m 2 , respectively. The adhesion strength maintains a decreasing trend along with the decreasing crystallite size. Considering the effect of the crystallite size, a new mechanism of the small current density deposition method is presented in this Letter. This Letter may contribute to improving the adhesion strength of the electrodeposited layer.

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

“…Table 1 shows that the compressive stress is big when the crystallite size was small in the experiments. Meanwhile, the practical adhesion energy is reduced by the compressive stress in the electroforming layer [7]. Generally, the bigger the crystallite size, the lower the compressive stress and Figure 1 Relational graph of practical adhesion energy against crystallite size the greater the practical adhesion strength will be.…”

“…These include the substrate surface, internal stress, hydrogen content in the film and the film thickness. Meanwhile, our previous work shows that the practical adhesion energy of the electroforming Ni layer on the Cu substrate is also influenced by the electroforming crystallite size [7]. Based on this, the equations between the electroforming crystallite size and the practical adhesion energy are investigated in this Letter.…”

“…The basic adhesion energy of film A on substrate B is [7] where W is the basic adhesion energy, and γ A and γ B are the surface energy of the coating A and substrate B, respectively. Δ H A in B is the enthalpy change upon solution of 1 M of A in an infinitely large reservoir of B.…”

“…The roughness of the Cu substrate was small ( R a < 0.04 μm). A powder X‐ray diffractometer (Empyrean, PANalytical Company, The Netherlands) was used to measure the electroforming crystallite size and an X‐ray diffractometer (Bruker D8 Discover) was applied to measure the compressive stress in the electroforming layer [7]. A scratch tester (CSR‐01, RHESCA Co. Ltd, Japan) was used to test the practical adhesion energy [12].…”

Biofield Energy Treatment: A Potential Strategy for Modulating Physical, Thermal and Spectral Properties of 3-Chloro-4-fluoroaniline

“…The decrease in crystallite size of treated sample could be ascribed to biofield treatment that may cause increase in compressive stress that leads to increase in dislocation density and decrease in crystallite size. Zhao et al showed that increase in compressive stress in the material causes decrease in crystallite size [24]. Moreover, Schicker et al reported that crystallite size is inversely proportional to the milling speed, thus increase in milling speed decreases the crystallite size [25,26] improve its reaction rate [30] and it could be utilized for the synthesis of pharmaceutical compounds.…”