Foster-Miller is developing a new, low-cost, high reliability, hermetic packaging technology for implantable electronics.  This technology platform is based on a remarkable new class of materials known as thermoplastic Liquid Crystal Polymers (LCPs). LCPs have a unique combination of properties that make them ideally suited for maintaining the high level of package performance required for implantable electronic systems, including:

• Extremely inert in a biological environment. We have demonstrated that LCP films can be used to fabricate flexible cables that can be subsequently passivated to provide a barrier to moisture and salt containing bodily fluids.
• Excellent electrical properties even up to millimeter wave frequencies (dielectric constant, 2.9; loss factor, 0.002 at 20 GHz).
• Extraordinary barrier properties, comparable to that of glass; LCPs are virtually impermeable to moisture, oxygen, and other gases and liquids.  LCP packages have passed the mil-spec helium leak test for package hermeticity.
• Low coefficient of thermal expansion (CTE) that can be tailored in the range of 0 to 30 ppm/ºC, offering the possibility of perfect CTE matching to silicon and galium arsenide devices.
• Very low moisture absorption, <0.02 percent by weight.
• Excellent dimensional stability (< 0.1 percent).

LCP substrates can accommodate bare silicon die and packaged components, with demonstrated compatibility with wire bonding and soldering. They have been used to fabricate microstructures, offering the potential of integrated microfluidics. Molded LCP lids can be sealed to the LCP interconnect substrate using thermoplastic welding techniques, thus creating a hermetic seal.

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