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Method for a nonlinear ground plane edge for folded flex packages

IP.com Disclosure Number: IPCOM000011742D
Publication Date: 2003-Mar-12
Document File: 3 page(s) / 39K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a nonlinear ground plane edge for folded flex packages. Benefits include improved performance and improved reliability.

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Method for a nonlinear ground plane edge for folded flex packages

Disclosed is a method for a nonlinear ground plane edge for folded flex packages. Benefits include improved performance and improved reliability.

Background

        � � � � � A solid reference plane can be placed on the groundside of the package. However, if the ground plane edge is linear and too close to the fold region, the package cracks along that edge (see Figure 1).

        � � � � � The conventional solution is to not use a ground plane for folded packages (see Figure 2).

Folded flexible tape is formed into a U-shape. Front-side chip scale packages (FSCSPs) have a polyimide core with 12-µm copper foil plated to both sides of the PI core. On the groundside, the supplier plates an additional 15 µm of Au to form vias. However, a requirement has been identified for a ground plane.

� � � � � At projected higher speeds, critical I/O and clock/strobe traces require controlled trace impedance for signal integrity in a small form factor. Providing the ground plane only near the fold creates an abrupt change in impedance for traces further from the fold.

General description

        � � � � � The disclosed method is a nonlinear ground plane edge for folded flex packages. This reference plane has a nonlinear edge to prevent tearing along its edge.

        � � � � � The key elements of the method include:

•        � � � � Standard folded flex tape package with a ground plane on one side

•        � � � � Nonlinear edge near the fold region

Advantages

        � �...