Micro-Cantilever Array With Electroplating Tin Bumps for Flip-Chip Bonding Technology

• Published in: IEEE transactions on components, packaging, and manufacturing technology (2011) packaging, and manufacturing technology (2011), 2023-12, Vol.13 (12), p.2040-2045
• Main Authors: Hu, Zihsong, Liou, Chengshiun, Tsou, Chingfu
• Format: Article
• Language: English
• Subjects: Arrays; Ball grid packaging; Bonding; Cantilever beam array; Chip carriers; Electrochemical deposition; Electrodes; Electronic packaging; electroplated tin bump; Electroplating; flip-chip; Flip-chip devices; Glass substrates; High density; Metal-metal bonding; micro-electro-mechanical system (MEMS); Microelectromechanical systems; Nickel; Plating; Structural beams; Tin
• ISSN: 2156-3950; 2156-3985
• DOI: 10.1109/TCPMT.2023.3339767

A Nickel (Ni) microcantilever beam array with tin (Sn) solder bumps has been designed for flip-chip bonding with high-density electrodes. Micro-electro-mechanical system (MEMS) technology and the micro-electroplating process were used in the fabrication process. Utilizing the out-of-plane deformation of the suspended microcantilever beam, the satisfied heights partially compensate the substrate curvature to ensure a high flip-chip bonding yield, thus, improving package quality in terms of electrical connections. To demonstrate this technique, this study developed a flip-chip carrier for a typical micro-LED array with a beam length of 70~\mu \text{m} and a bump height of 2~\mu \text{m} . The measurement results revealed that the displacement of the microcantilever beam was approximately 0.8~\mu \text{m} when a 500~\mu \text{N} force was applied on top of the tin bump. When a glass substrate directly mounts to the flip-chip carrier through the tin bump at a heat reflow of 270 °C, most of the tin bumps successfully melt and solidify, which results in good bonding performance. These results revealed that the proposed approach could be applied to the wafer-level packaging process with high-density ball grid array electrodes.