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Browse Prior Art Database

Lightguides and Optical Storage Elements in Polyimide

IP.com Disclosure Number: IPCOM000039832D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Franke, H: AUTHOR

Abstract

Optical interconnection is increasingly important as it becomes necessary to bring optical connections onto the electronic IC card to electro-optic chips which do the electrical-to-optical and optical- to-electrical conversions. This will be done for packaging-density, speed, and reliability reasons. In this environment, it is desirable to be able to process lightguides onto the IC cards and boards using materials and processes compatible with the IC packaging industry. Polyimide is a solution-coated, high temperature, electronic packaging material already in popular use in the IC industry. Techniques are described herein which provide the ability to guide light in this material over centimeters of distance. Also, the guides can be made to withstand processing up to 200oC.

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Lightguides and Optical Storage Elements in Polyimide

Optical interconnection is increasingly important as it becomes necessary to bring optical connections onto the electronic IC card to electro-optic chips which do the electrical-to-optical and optical- to-electrical conversions. This will be done for packaging-density, speed, and reliability reasons. In this environment, it is desirable to be able to process lightguides onto the IC cards and boards using materials and processes compatible with the IC packaging industry. Polyimide is a solution-coated, high temperature, electronic packaging material already in popular use in the IC industry.

Techniques are described herein which provide the ability to guide light in this material over centimeters of distance. Also, the guides can be made to withstand processing up to 200oC. For proper fabrication of these guides, it is necessary to drive all the solvent from the film prior to the high temperature processing, as solvent boiling introduces voids (light scattering centers) into the films.

The techniques also permit low loss lightguiding in polyimide which is on a layer of silicone which is in turn on a ceramic substrate (a popular carrier for electronic ICs). According to the techniques, optical waveguides are formed in polyimide polymers, where the guides have the solvents removed by curing and where a mix of polymers is used for long time curing and high temperature stability. Also, the guide has a cladding of lower index, high temperature polymer, such as silicone, which can act as a buffer between the guide and a light-absorbing or -scattering substrate or superstrate. Related passive optical elements, such as beam splitters or prisms, which are formed by putting high index polymers on low index polymers, can also be fabricated using the above processing techniques. Optical storage elements in polyimide can be formed by optical recording of refractive index patterns in the polyimide. It is desirable to be able to write two-dimensional lightguiding paths into the planar lightguide material, using an optical exposing technique (similar to the photolithographic techniques used in the IC industry), if possible. For the polymers PMMA and polycarbonate much work has been done concerning altering of refractive index by UV lithography. The obtained refractive index changes were usually of the order of several 10-3, recently a change of up to 5x10-2 was reported for PMMA
[1]. However, these materials are not compatible with the...