Browse Prior Art Database

Post Folding Trace Encapsulation for FSBGA

IP.com Disclosure Number: IPCOM000016801D
Publication Date: 2003-Jul-16
Document File: 2 page(s) / 61K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that encapsulates the exposed traces in the fold region of FSBGA packages. Benefits include prevention of bHAST failures and protection against contamination and corrosion on the traces.

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Post Folding Trace Encapsulation for FSBGA

Disclosed is a method that encapsulates the exposed traces in the fold region of FSBGA packages. Benefits include prevention of bHAST failures and protection against contamination and corrosion on the traces.

Background

BHAST failures occur during substrate level reliability testing in FSBGA. In the folded stacked configuration, the traces that are routed through the fold region remain exposed to the environment, making them susceptible to corrosion, FM, and migration failures. Covering these traces with solder mask material may impede the foldability of the substrate. Currently, the problem is not addressed; current packages leaves the traces exposed (see Figure 1).

General Description

The disclosed method mitigates migration failures by encapsulating the traces with either solder mask epoxy compound or die encapsulation mold compound, while allowing the package to be folded using the current design (see Figure 2).

The disclosed method adds a process step during assembly. This step involves injection of a thermal cure epoxy into the opening at the edge of the fold region. The epoxy is injected all the way through the fold region to the other side. As an added benefit, the epoxy in the fold region relieves stress in the fold joint.

A second implementation applies the epoxy as a bead in the fold region just before the folding step. When the package is folded, the epoxy creates a conformal coating in the fold region. A thermal cure af...