Influence of current density on the interfacial bond strength of electroformed layers

With the development of MEMS technology, the demand of multilayer or moveable micro-metal devices fabricated by microelectroforming is growing. The quality and life of the devices are seriously restricted by interfacial bond strength between two electroformed layers. In this Letter, a novel method to control the interfacial bond strength by adjusting the current density of microelectroforming is presented. On the basis of microelectroforming experiment, the quantitative measurement method of the interfacial bond strength by the scratch test, the effect of current density on interfacial bond strength and its mechanism are investigated. The experimental result indicates that within the range of chosen current densities, the bond strength keeps a decreasing trend along with the increase of current density, and there is a sharp decline when current density is between 0.4 and 0.6 A/dm². The adhesion work at 0.4 A/dm² is improved by 69.1% compared with that at 1.0%A/dm². This phenomenon is discussed with the partial discharge theory and the relationship between current density and overpotential. The method presented in this Letter, which is simple, efficient and economical, can improve the qualified rate of microdevices and prolong their life.