We report here a successful demonstration of a flip-chip packaging approach for a microelectromechanical systems (MEMS) device with in-plane movable microelectrodes implanted in a rodent brain. The flip-chip processes were carried out using a custom-made apparatus that was capable of the following: creating Ag epoxy microbumps for first-level interconnect; aligning the die and the glass substrate; and creating nonhermetic encapsulation (NHE). The completed flip-chip package had an assembled weight of only 0.5 g significantly less than the previously designed wire-bonded package of 4.5 g. The resistance of the Ag bumps was found to be negligible. The MEMS microelectrodes were successfully tested for its mechanical movement with microactuators generating forces of 450 with a displacement resolution of 8.8 . An NHE on the front edge of the package was created by patterns of hydrophobic silicone microstructures to prevent contamination from cerebrospinal fluid while simultaneously allowing the microelectrodes to move in and out of the package boundary. The breakdown pressure of the NHE was found to be 80 cm of water, which is significantly (4.5-11 times) larger than normal human intracranial pressures. Bench top tests and in vivo tests of the MEMS flip-chip packages for up to 75 days showed reliable NHE for potential long-term implantation.

中文翻译：

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可植入MEMS器件倒装芯片的封装和非气密封装技术

我们在此报告成功演示了微机电系统 (MEMS) 设备的倒装芯片封装方法，该设备具有植入啮齿动物大脑的平面内可移动微电极。倒装芯片工艺是使用定制设备进行的，该设备具有以下功能：创建用于一级互连的 Ag 环氧树脂微凸点；对准芯片与玻璃基板；并创建非气密封装 (NHE)。完成的倒装芯片封装的组装重量仅为 0.5 克，明显小于先前设计的 4.5 克引线键合封装。发现 Ag 凸块的电阻可以忽略不计。MEMS 微电极成功地测试了其机械运动，微致动器产生了 450 的力，位移分辨率为 8.8。封装前缘的 NHE 由疏水性有机硅微结构图案创建，以防止脑脊液污染，同时允许微电极移入和移出封装边界。发现 NHE 的击穿压力为 80 厘米水柱，比正常人的颅内压显着（4.5-11 倍）大。长达 75 天的 MEMS 倒装芯片封装的台式测试和体内测试表明，NHE 可用于潜在的长期植入。5-11 倍）大于正常人的颅内压。长达 75 天的 MEMS 倒装芯片封装的台式测试和体内测试表明，NHE 可用于潜在的长期植入。5-11 倍）大于正常人的颅内压。长达 75 天的 MEMS 倒装芯片封装的台式测试和体内测试表明，NHE 可用于潜在的长期植入。