Hermetic glass soldered micro-packages for a vision prosthesis

Abstract

Micro-packages based on alumina ceramics hermetically sealed with glass solder were fabricated and tested over a 1.5 years period under accelerated aging at 85 °C. A device for sealing the 1.2 mm high, and ø10mm packages while cooling the critical centre of the package containing the electronics was developed. Heating of the rim up to 550 °C while maintaining the package centre below 300°C was successful, allowing a symmetrical heating of the device during the sealing procedure. The fabricated packages with an inner volume of 0.05 cc were backfilled with helium and tested for hermeticity with a fine leak tester. Samples passing the fine leak (1•10(-12) atm•cc/s) test were attached to a larger chamber containing a humidity sensor. Some devices covered in PDMS and some directly exposed were stored at 85 °C in water to measure the humidity intrusion into the device due to deterioration of glass solder. 1 out of the 8 successfully fabricated devices failed after 5 years extrapolated lifetime. Two of the devices have kept constant humidity levels while others gradually rise. Nevertheless, 7 out of 8 have maintained a level below 17,000 ppm humidity. Furthermore, the deterioration of glass solder was electrically and optically studied over a year's period showing no corrosion of glass if properly coated in PDMS.

Selective laser sintering of glass-ceramic bonds using a defocused Nd:YAG laser

“…The seal dimensions achieved suggest that 100 μm to 1 mm scale bonds will be possible, larger than present state-of-theart chip scale packaging, but comparable with solder seals used for hybrid ceramic packaging. Avoiding a conductive seal ring or package will reduce losses for implant wireless receiver coils on or inside hermetic packages [2]. To develop this process for use in a medical device we are investigating the strength and hermeticity of the bonds, alternative commercial glass sealing pastes, possible glass paste dissolution in body fluids, and integrating conductive metal feedthroughs across the glass-ceramic seal.…”

“…Long-term implantable devices may require hermetically sealed packages to protect active components [1]. Metal packages, or conductive seal rings are problematic for integrating inductively coupled power-data links inside packages [2], [3]. Therefore, non-conductive hermetic seals are sought.…”

“…One such approach is using a sealing glass material in place of a solder seal ring. Glass seals have been achieved by furnace-bonding samples; however, this also heats active components in the package to temperatures in the range of 500 °C [2], [4]. Glass-glass welding using laser-targeted heating to bond surface-applied glass-frit paste is promising to create rapid miniature seals within only localized heating as the seal.…”

Reliability of spring interconnects for high channel-count polyimide electrode arrays

“…The power modules, data acquisition or sense/stimulation circuitry and telemetry units along with the antenna(s) should be an integral part of the compact implant system. Though the implant electronics are sealed on the component or system level [3][4][5], their interconnections interface with the electrode arrays is usually prone to attack from the physiological environment. This issue is not very critical for implants with stiff electrode substrates (such as silicon) since the electronics can be monolithically integrated or can be bonded and sealed on the silicon substrate reliably because of well-established technology [6,7].…”