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High Purity Polyimide Undercoat to Enhance Magnetic Properties and Corrosion Protection for Thin and Thick Film Recording Disks

IP.com Disclosure Number: IPCOM000049048D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Duran, J: AUTHOR [+4]

Abstract

The present aluminum substrate used for recording disks has a very large grain size which induces corrosion in the device structure. Also, the undercoat material used to protect the surface from corrosion is highly stressed and causes non-reproducibility of the magnetic properties (metal-to-metal contact diffusion and galvanic coupling).

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High Purity Polyimide Undercoat to Enhance Magnetic Properties and Corrosion Protection for Thin and Thick Film Recording Disks

The present aluminum substrate used for recording disks has a very large grain size which induces corrosion in the device structure. Also, the undercoat material used to protect the surface from corrosion is highly stressed and causes non-reproducibility of the magnetic properties (metal-to-metal contact diffusion and galvanic coupling).

High purity polyimide materials will eliminate the effect of the large grain size of the aluminum substrate surface and, in addition, will greatly enhance magnetic properties and reproducibility.

It has been demonstrated that no adhesion promoter is required for high purity polyimide to demonstrate excellent adhesion to aluminum substrates. Special low temperature precure process and final cure insure excellent adhesion with no thermal or other demage to the disk substrate. Excellent passivation and leveling is provided with a pinhole-free layer.

Films of 7,000-20,000 Angstroms thick high purity polyimide, after a 150-hour test in multi-gas accelerated corrosion chamber, resulted in excellent protection of the aluminum substrate and no deterioration of adhesion.

Adhesion tests performed with a Quad Sebastian I adhesion tester showed pull test values in excess of 5000 psi. In all tests, pin-epoxy shear was the failure mode with no polyimide-aluminum bond separation. The proposed undercoat material requires minimum capital equipment expense and low operating expense. Equipment in current use for disk manufacturing is applicable to the spin coating of polyimide.

Unlike Stellite cryetalline material, which adversely affects the magnetic properties and reproducibility of the FeCoCr recording layer, the polyimide provides an amorphous surface which is ideally suited for high H(c) materials. Galvanic isola...