Flexible chip-scale package and interconnect for implantable MEMS movable microelectrodes for the brain

Nathan Jackson, Jitendran Muthuswamy

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

We report here a novel approach called microelectromechanical systems (MEMS) microflex interconnect (MMFI) technology for packaging a new generation of Bio-MEMS 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 μm 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 mΩ 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 mΩ 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 Bio-MEMS devices.

Original languageEnglish (US)
Pages (from-to)396-404
Number of pages9
JournalJournal of Microelectromechanical Systems
Volume18
Issue number2
DOIs
StatePublished - 2009

Fingerprint

Chip scale packages
Microelectrodes
MEMS
Brain
Packaging
Gold
Rivets
Thermal shock
Thermal cycling
Substrates
Contact resistance
Polyimides
Atmospheric humidity
Tissue
Aluminum
Thin films

Keywords

  • Bio-microelectromechanical systems (MEMS)
  • Biomedical microdevices
  • Brain implants
  • Microflex technology
  • Neural prostheses
  • Polyimide

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Mechanical Engineering

Cite this

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abstract = "We report here a novel approach called microelectromechanical systems (MEMS) microflex interconnect (MMFI) technology for packaging a new generation of Bio-MEMS 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 μm 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 mΩ 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 mΩ 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 Bio-MEMS devices.",
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