Fabrication of an Electrode Array with Thick Film Platinum Wire Using Laser Micromachining

Abstract

 

Purpose:

 

To develop an wiring technology of electrode array with high reliability, low impedance and high bondability to other components for retinal prostheses.

 

Methods:

 

Wiring pattern of an electrode array were formed by cutting a 20µm-thick platinum foil by femtosecond laser irradiation. The widths of line and spaces between lines were 39µm and 38µm respectively. Supporting structures were simultaneously formed so that each wire was not dissected out after laser cutting process (see Fig.1). After depositing 5µm-thick parylene for insulation, connection pads were exposed by removing parylene focally by reactive ion etching (RIE). Bulk electrodes, formed by mechanical machining (Terasawa et. al., ARVO 2008), were welded to the exposed pads. After removing supporting structures by laser machining, a substrate was formed by depositing 30µm-thick parylene onto the wiring pattern.

 

Results:

 

Femtosecond laser machining enabled us to form a 40µm-witdth, 20µm-thick platinum wire from platinum foil. Parylene removal of a connection pad was achieved by RIE using metal mask (made of 30µm-thick stainless foil). Bulk platinum electrodes were welded to wires reliably with resistance welding. Tips of electrodes were successfully exposed by using the welding jig, into which stimulation electrodes were buried, as a sacrificial layer in succeeding parylene deposition process.

 

Conclusions:

 

We succeeded in forming platinum thick film wiring pattern as well as bonding wires to stimulation electrodes. We are planning reliability tests in the next step.  

 

Keywords: retina