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Selectively Sealing Porosity and Cracks in Anodized Aluminum for Dielectric Protection

IP.com Disclosure Number: IPCOM000036323D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Imken, RL: AUTHOR

Abstract

Disclosed is a method for selectively sealing cracks in anodized alumi- num circuit cards by using an organic material which polymerizes when exposed to ultraviolet light. Thick anodic coatings on aluminum panels have good potential for electronic card applications by offering high voltage breakdown and excellent thermal dissipation. However, the nature of the anodic growth on the base aluminum yields cracks in the anodic layer at sharp transitions, such as via holes and card edges. These cracks extend to the aluminum core of the anodized panel such that circuitry over such cracks can easily short to the core.

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Selectively Sealing Porosity and Cracks in Anodized Aluminum for Dielectric Protection

Disclosed is a method for selectively sealing cracks in anodized alumi- num circuit cards by using an organic material which polymerizes when exposed to ultraviolet light. Thick anodic coatings on aluminum panels have good potential for electronic card applications by offering high voltage breakdown and excellent thermal dissipation. However, the nature of the anodic growth on the base aluminum yields cracks in the anodic layer at sharp transitions, such as via holes and card edges. These cracks extend to the aluminum core of the anodized panel such that circuitry over such cracks can easily short to the core.

The technique disclosed here fills cracks with an organic material which reacts when exposed to ultraviolet (UV) light, forming an electri- cally insulative barrier. The process is selective since areas to be left uncoated can be masked or shielded from the UV during the time of UV exposure. A subsequent solvent rinse of the coated card will remove uncured sealant. Penetration of sealant into cracks can be facilitated by coating in a vacuum impregnation process. In addition, certain UV sealants may be heated to lower viscosity and promote penetration. Sealant-free areas of the card can be beneficial in situations where electrical contact to exposed aluminum is desirable.

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