We report here a novel approach called microelectromechanical systems (MEMS) microflex interconnect (MMFI) technology for packaging a new generation of bioMEMS devices that involve movable microelectrodes implanted in brain tissue. MMFI addresses the need for the following: (1) operating space for movable parts and (2) flexible interconnects for mechanical isolation. We fabricated a thin polyimide substrate with embedded bond pads, vias, and conducting traces for the interconnect with a backside dry etch, so that the flexible substrate can act as a thin-film cap for the MEMS package. A double-gold-stud-bump rivet-bonding mechanism was used to form electrical connections to the chip and also to provide a spacing of approximately 15-20 mum for the movable parts. The MMFI approach achieved a chip-scale package that is lightweight and biocompatible and has flexible interconnects and no underfill. Reliability tests demonstrated minimal increases of 0.35, 0.23, and 0.15 mOmega in mean contact resistances under high humidity, thermal cycling, and thermal shock conditions, respectively. High-temperature tests resulted in increases of > 90 and ~ 4.2 mOmega in resistance when aluminum and gold bond pads were used, respectively. The mean time to failure was estimated to be at least one year under physiological conditions. We conclude that MMFI technology is a feasible and reliable approach for packaging and interconnecting bioMEMS devices.

中文翻译：

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用于大脑植入式 MEMS 可移动微电极的柔性芯片级封装和互连

我们在这里报告了一种称为微机电系统 (MEMS) 微柔性互连 (MMFI) 技术的新方法，用于封装涉及植入脑组织的可移动微电极的新一代 bioMEMS 设备。MMFI 解决了以下需求：(1) 可移动部件的操作空间和 (2) 用于机械隔离的柔性互连。我们制造了一个薄的聚酰亚胺基板，带有嵌入式焊盘、通孔和用于互连的导电迹线，背面干蚀刻，以便柔性基板可以作为 MEMS 封装的薄膜帽。双金钉凸点铆钉接合机制用于形成与芯片的电气连接，并为可移动部件提供大约 15-20 微米的间距。MMFI 方法实现了轻量级和生物相容性的芯片级封装，具有灵活的互连且无底部填充。可靠性测试表明，在高湿度、热循环和热冲击条件下，平均接触电阻分别增加了 0.35、0.23 和 0.15 mΩ。当使用铝和金焊盘时，高温测试分别导致电阻增加 > 90 和 ~ 4.2 mΩ。在生理条件下，估计失败的平均时间至少为一年。我们得出的结论是，MMFI 技术是一种用于封装和互连 bioMEMS 设备的可行且可靠的方法。分别是热循环和热冲击条件。当使用铝和金焊盘时，高温测试分别导致电阻增加 > 90 和 ~ 4.2 mΩ。在生理条件下，估计失败的平均时间至少为一年。我们得出的结论是，MMFI 技术是一种用于封装和互连 bioMEMS 设备的可行且可靠的方法。分别是热循环和热冲击条件。当使用铝和金焊盘时，高温测试分别导致电阻增加 > 90 和 ~ 4.2 mΩ。在生理条件下，估计失败的平均时间至少为一年。我们得出的结论是，MMFI 技术是一种用于封装和互连 bioMEMS 设备的可行且可靠的方法。