Enhancing the adhesion strength of micro electroforming layer by ultrasonic agitation method and the application

Abstract

Micro electroforming is widely used for fabricating micro metal devices in Micro Electro Mechanism System (MEMS). However, there is the problem of poor adhesion strength between micro electroforming layer and substrate. This dramatically influences the dimensional accuracy of the device. To solve this problem, ultrasonic agitation method is applied during the micro electroforming process. To explore the effect of the ultrasonic agitation on the adhesion strength, micro electroforming experiments were carried out under different ultrasonic power (0W, 100W, 150W, 200W, 250W) and different ultrasonic frequencies (0kHz, 40kHz, 80kHz, 120kHz, 200kHz). The effects of the ultrasonic power and the ultrasonic frequency on the micro electroforming process were investigated by polarization method and alternating current (a.c.) impedance method. The adhesion strength between the electroforming layer and the substrate was measured by scratch test. The compressive stress of the electroforming layer was measured by X-ray Diffraction (XRD) method. The crystallite size of the electroforming layer was measured by Transmission Electron Microscopy (TEM) method. The internal contact surface area of the electroforming layer was measured by cyclic voltammetry (CV) method. The experimental results indicate that the ultrasonic agitation can decrease the polarization overpotential and increase the charge transfer process. Generally, the internal contact surface area is increased and the compressive stress is reduced. And then the adhesion strength is enhanced. Due to the different depolarization effects of the ultrasonic power and the ultrasonic frequency, the effects on strengthening the adhesion strength are different. When the ultrasonic agitation is 200W and 40kHz, the effect on strengthening the adhesion strength is the best. In order to prove the effect which the ultrasonic agitation can improve the adhesion strength of the micro devices, micro pillar arrays were fabricated under ultrasonic agitation (200W, 40kHz). The experimental results show that the residual rate of the micro pillar arrays is increased about 17% by ultrasonic agitation method. This work contributes to fabricating the electroforming layer with large adhesion strength.

Influence of ultrasonic combined supercritical-CO2 electrodeposition process on copper film fabrication: Electrochemical evaluation

“…This is due to the effect of microbubbles explosion from the supercritical CO 2 affects nucleation growth during the electrodeposition. Notably, the observed diffraction pattern in US-SC-CO 2 -15 W cm −2 displays the most significant full width at half maximum (FWHM), which indicated that ultrasonic agitation would lead to the smallest grain size [16] , [23] , [24] . Similar to the previous reports, the grain sizes are calculated from the Scherrer equation [38] , [39] , [40] , [41] , [42] .…”

“…In recent decades, ultrasonic-assisted electrodeposition has been widely used to improve the quality of electrodeposited materials [22] , [23] , [24] . It is due to the fact of high energy from the ultrasonic irradiation that creates cavitation effects such as mass transport processes, acoustic streaming, surface activation, and micro jetting formation [25] .…”

Current Challenges and Innovative Developments in Hydroxyapatite-Based Coatings on Metallic Materials for Bone Implantation: A Review

“…The poor coating layers will exfoliate and create serious effects during the tissue healing process. The coating pieces will leave the surface due to poor strength and affect the surrounding body parts [86,87]. The coating on metallic substratesis widely used to make it bio-compatible and bio-active.…”

Corrosion Behavior of the Nickel/nickel Interface During the Copper Sacrificial Layer Releasing Process in Micro-Electroforming

“…Weak interface bonding can even lead to the warpage or delamination of electrodeposited layers and nally result in the fabrication failure. At present, many methods have been adopted to improve the adhesion strength, including surface activation prior to plating [8], regulating electrodeposit current density [9] and ultrasound-assisted electrodeposit method [10]. However, post-processes, photoresist removal and sacri cial layer release, also have great effects on the interfacial bonding strength, which are rarely investigated.…”