Design and characterization of a biocompatible packaging concept for implantable electronic devices

Abstract

A biocompatible packaging process for implantable electronic systems is described, combining biocompatibility and hermeticity with extreme miniaturization. In a first phase of the total packaging sequence, all chips are encapsulated in order to realize a bi-directional diffusion barrier preventing body fluids to leach into the package causing corrosion, and preventing IC materials such as Cu to diffuse into the body, causing various adverse effects. For cost effectiveness, this hermetic chip sealing is performed as post-processing at wafer level, using modifications of standard clean room (CR) fabrication techniques. Well known conductive and insulating CR materials are investigated with respect to their biocompatibility, diffusion barrier properties and sensitivity to corrosion. In a second phase of the packaging process, all chips of the final device should be electrically connected, applying a biocompatible metallization scheme using eg. gold or platinum. For electrodes being in direct contact with the tissue after implantation, IrOx metallization is proposed. Device assembly is the final packaging step, during which all system components such as electronics, passives, a battery,… will be interconnected. To provide sufficient mechanical support, all these components are embedded using a biocompatible elastomer such as PDMS.

Fully Integrated Biochip Platforms for Advanced Healthcare

“…As a consequence, a bi-directional diffusion barrier is essential: body and implant must be isolated from each other. Moreover, biocompatible materials must be used for the fabrication of this diffusion barrier and the packaging of the total device [ 222 , 223 ]. The most conventional device package consists of a titanium box, equipped with feed-throughs for sensors.…”

Mechanical Characterization and Analysis of Different-Type Polyimide Feedthroughs Based on Tensile Test and FEM Simulation for an Implantable Package

“…In existing commercial medical devices such as pacemakers, titanium (Ti) boxes are often used to ensure hermetic and biocompatible packaging of the microelectronic device [6]. While Ti boxes are well-known hermetic implant packaging materials, they evoke pronounced foreign body reactions (FBRs) upon implantation, resulting in encapsulation by a thick layer of fibrous tissue that might decrease the sensitivity of the implanted sensor [7]. Furthermore, mechanical mismatches between the Ti box and local tissues may cause chronic discomfort to the patient.…”