Improved wear resistance of cemented carbide impact needle under high frequency micro-amplitude impact treated by high current pulsed electron beam

Abstract

Assembly and packaging technology is one of the most critical factors that restrict the development of microelectromechanical systems (MEMS), including chips and other devices. Dispensing robot is a key high-end equipment in MEMS packaging. Its core component, WC-Co impact needle, is limited by fretting wear and deformation, leading to reduced service accuracy and life, which is the most important cause of failure. Impact fretting wear frequently occurs in micro-nano mechanical systems and has been widely studied. However, the combined high frequency (∼300 HZ) and micro impact amplitude (∼120 μm) wear behaviors such as WC-Co impact needle with ultrafine grain (∼100 nm) is rarely concerned. To further understand the influence of impact frequency and impact velocity on the wear rate of impact needle, dispensing experiments were designed and the wear mechanism was investigated. Results indicated that the impact velocity has more influence on the wear rate of impact needle than the impact frequency. In addition, a high-current pulsed electron beam (HCPEB) surface treatment method which can effectively increase the wear resistance of impact needle was proposed. After HCPEB treatment, the abrasion loss was reduced by 44% compared to the untreated one at the same impact frequency and different impact velocities, while the abrasion loss was reduced by 52% compared to the untreated one at the same impact velocity and different frequencies. These can be attributed to the fact that HCPEB treatment decreased the grain size of WC-Co cemented carbide impact needle and promoted WC phase transition, leading to an increase in microhardness.