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Prevention of Metal Migration through Insulators

IP.com Disclosure Number: IPCOM000092411D
Original Publication Date: 1966-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

DeStafeno, JJ: AUTHOR [+3]

Abstract

The addition of small amounts of metal sulphides to solid insulation materials is effective in inhibiting metal migration through them.

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Prevention of Metal Migration through Insulators

The addition of small amounts of metal sulphides to solid insulation materials is effective in inhibiting metal migration through them.

Certain metals, especially silver, show a strong tendency to migrate through solid insulating media in the presence of intense electric fields, such as from contact to contact through a solid insulating medium. The generally positive metal ions migrate from the positive, anodic, contact or electrode towards the negative electrode. As metal, or in some cases, conducting metal compounds, accumulate at the cathode, the deposit formed grows, reducing effective gap width, leading to decreased insulation resistance, increased leakage current and increased rate of migration. The process continues until the gap is sufficiently narrowed leading to melting or burning of the insulator, or complete dielectric breakdown.

To prevent migration, approximately 2%, by weight, of certain metal sulphides such as Sb(2)S(3), SnS(2), In(2)S(3), are added to the host insulating material prior to pressing, molding, forming or curing of same. These are chemically inert in themselves, but when in contact with the active metal ions form stable, insoluble metal salts thus tying up the active metal. The mechanical and electrical properties of the host insulating material remain unchanged, while migration through the insulation is significantly reduced, even under 95-100% relative humidity, high DC electric fiel...