ENHANCED SEAL INTERFACE

Publishing Venue

Motorola

Related People

Timothy Fisher: AUTHOR [+1][-]

Keith Meny: AUTHOR

Abstract

Housing/cover plate seal interfaces that protect del- icate electronics must resist volatile chemicals, abrasion, and even submersion in some cases. These specitica- tions require an extremely robust seal. For many appli- cations, a wet-seal, which is dispensed in such a way that it penetrates all gaps prior to curing, is the best choice. Unfortunately, the most robust wet-seal materials are not always compatible with Design for Manutacturabiity due to their long cure schedules, which can drastically increase process cycle time. However, the cure times of sealants that polymerize upon exposure to the ambient (air, humidity, etc.) can be reduced through proper inter- face design. The seal design must also be compatible with the mechanical fastening technique. Crimping of the housing to the cover plate minimizes the number of parts required while providing a reliable fastening method.

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MOTOROLA INC. Technical Developments Volume 17 December 1992

ENHANCED SEAL INTERFACE

by Timothy Fisher and Keith Meny

   Housing/cover plate seal interfaces that protect del- icate electronics must resist volatile chemicals, abrasion, and even submersion in some cases. These specitica- tions require an extremely robust seal. For many appli- cations, a wet-seal, which is dispensed in such a way that it penetrates all gaps prior to curing, is the best choice. Unfortunately, the most robust wet-seal materials are not always compatible with Design for Manutacturabiity due to their long cure schedules, which can drastically increase process cycle time. However, the cure times of sealants that polymerize upon exposure to the ambient (air, humidity, etc.) can be reduced through proper inter- face design. The seal design must also be compatible with the mechanical fastening technique. Crimping of the housing to the cover plate minimizes the number of parts required while providing a reliable fastening method.

  Generally, a channel feature is designed into the hous- ing. This feature captures most of the sealant while the rest penetrates the gaps between the housing and the cover plate (see Figure I). This design minimizes cure times by directly exposing some of the sealant to the ambient; however, the cover plate may deform into the channel and displace the sealant in the crimped areas. Thus, a support detail is needed in the crimp areas in order to eliminate this occurr...