Wafer-level Cu–Sn micro-joints with high mechanical strength and low Sn overflow. (6th August 2015)

• Record Type: Journal Article
• Authors: Duan, Ani; Luu, Thi-Thuy; Wang, Kaiying; Aasmundtveit, Knut; Hoivik, Nils
• Is Part Of: Journal of micromechanics and microengineering. Volume 25:Number 9(2015:Sep.)
• Publication Date: 2015-08-06
• Subjects: wafer-level process -- Cu/Sn SLID -- microelectromechnical systems (MEMS); Microelectromechanical systems -- Periodicals; Micromechanics -- Periodicals; 621.38105
• DOI: 10.1088/0960-1317/25/9/097001
• Languages: English
• ISSNs: 0960-1317

Abstract

Abstract: In this paper, we report wafer-level bonding using solid-liquid inter-diffusion (SLID) processes for fabricating micro-joints Cu–Sn at low temperature (270 °C). The evolution of multilayer Cu/Sn to micro-joint alloys has been characterized by optical microscopy and mechanical die-shear testing. The Cu–Sn joints with line width from 80 to 200 μ m prove to be reliable packaging materials for bonding vacuum micro-cavities with controllable Sn overflow, as well as high mechanical strength (>70 MPa). A thermodynamic model has been performed to further understand the formation of Cu–Sn intermetallic alloys. There are two important findings for this work: 1) Using a two-step temperature profile may significantly reduce the amount of Sn overflow; 2) for packaging, a bond frame width greater than 80 μ m will result in high yield.