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Polymeric Encapsulation of Flex Substrate Fold Region

IP.com Disclosure Number: IPCOM000012944D
Publication Date: 2003-Jun-11
Document File: 4 page(s) / 68K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses a non-conductive polymeric adhesive, which serves the dual purpose of forming an encapsulating barrier for exposed substrate metal traces in the fold region as well as provide mechanical strength to the folded portion of the substrate.

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Polymeric Encapsulation of Flex Substrate Fold Region

Disclosed is a method that uses a non-conductive polymeric adhesive, which serves the dual purpose of forming an encapsulating barrier for exposed substrate metal traces in the fold region as well as provide mechanical strength to the folded portion of the substrate.

Background

The current process requires a very tight fold radius in the flex substrate without the presence of mechanical damage. In addition, the process is susceptible to corrosion and contamination of the exposed metal traces in the fold region (see Figures 1 through 3). Presently, the current state of the art does the following:

 

  • Covers the fold region of a flex substrate with solder mask (which increases the minimum fold radius).
  • Omits the solder mask entirely or uses strips of solder mask that run parallel to the fold axis in the fold region, which results in exposed metal traces that are prone to corrosion, metal migration, and contamination. The use of solder mask strips also results in a non-uniform bend radius because of the varying section thickness in the fold region.
  • Neglects the problem of a mechanically fragile folded substrate edge.

General Description

The disclosed method uses a substrate manufactured without the solder mask layer in the fold region, and a non-conductive polymeric adhesive on top of the mold compound as well as on top of the fold region of the substrate (see Figure 4). Sufficient adhesive is dispensed in the fold region to ensure that the cavity is completely filled once the fold is complete. The fold and cure of the assembly results in the complete encapsulation of the fold region with the reduce...