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Packaging and Non-Hermetic Encapsulation Technology for Flip Chip on Implantable MEMS Devices
Jemmy Sutanto1, Sindhu Anand1, Arati Sridharan1
1School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85287-9709 USA.
Journal of Microelectromechanical Systems : a Joint IEEE and ASME Publication on Microstructures, Microactuators, Microsensors, and Microsystems
|January 17, 2014
Summary
A novel flip-chip packaging method enables microelectromechanical systems (MEMS) devices with movable microelectrodes for brain implantation. This lightweight, non-hermetic encapsulation ensures reliable function and protection in vivo.
Area of Science:
- Biomedical Engineering
- Materials Science
- Neuroscience
Background:
- Implanting microelectromechanical systems (MEMS) devices in the brain requires robust packaging.
- Traditional wire-bonded packaging is heavy and bulky, limiting long-term implantation.
- Existing encapsulation methods may impede the necessary movement of microelectrodes.
Purpose of the Study:
- To demonstrate a novel flip-chip packaging approach for MEMS devices with in-plane movable microelectrodes.
- To develop a lightweight and reliable packaging solution for brain implantation.
- To ensure the functionality and protection of MEMS devices in vivo.
Main Methods:
- A custom apparatus was used for flip-chip processing, including Ag epoxy microbump creation, die-to-substrate alignment, and non-hermetic encapsulation (NHE).
- Hydrophobic silicone microstructures were patterned to create the NHE, preventing contamination while allowing electrode movement.
- The flip-chip package's weight, interconnect resistance, microelectrode mechanical performance, and NHE breakdown pressure were evaluated.
Main Results:
- The flip-chip package weighed 0.5 g, significantly lighter than wire-bonded alternatives (4.5 g).
- Ag bumps exhibited negligible resistance, and MEMS microelectrodes demonstrated precise mechanical movement (450 μN force, 8.8 μm/step resolution).
- The NHE withstood 80 cm of water breakdown pressure, exceeding human intracranial pressure, and showed reliable performance in vivo for up to 75 days.
Conclusions:
- The demonstrated flip-chip packaging approach offers a lightweight, reliable solution for MEMS devices with movable microelectrodes.
- The developed non-hermetic encapsulation effectively protects against contamination while permitting essential electrode motion.
- This technology holds promise for advanced, long-term neural interfaces and brain implantation applications.
