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Browse Prior Art Database

Anchored Mold Gate Design

IP.com Disclosure Number: IPCOM000130472D
Publication Date: 2005-Oct-25
Document File: 3 page(s) / 562K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that adds plated through holes (PTH) to the mold gate of the plastic ball grid array (PBGA) substrate. Benefits include eliminating mold gate peel-off and increasing the structural strength of the mold gate.

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Anchored Mold Gate Design

Disclosed is a method that adds plated through holes (PTH) to the mold gate of the plastic ball grid array (PBGA) substrate. Benefits include eliminating mold gate peel-off and increasing the structural strength of the mold gate.

Background

Mold gate peeling occurs after the mold encapsulation process of PBGA packages, and is caused either by adhesion problems induced during the manufacture of the substrate (see Figure 1), or from mechanical flexure during the molding of the PBGA assembly (see Figure 2). 

The mechanical flexure from the mold cull removal process does not induce mold gate peel-off if there is a good alignment between the substrate strip and the mold cavities. Any misalignment between the two causes the formation of an unnecessary bond between the mold cull and the solder resist of the substrate. Mold cull removal is done through flexing the strips, thereby inducing the substrate cracks that may lead to the mold gate peel-off.

Currently, the copper-to-polymer adhesion problem is solved by roughening the polymer base

(i.e. BT epoxy pre-preg material) to increase the effective surface area of the plating, and by

optimizing the current density during the plating process of the substrate.

Alignment problems between the mold cavity and the substrate are currently addressed by

preventive maintenance checks on the equipment to minimize the effects of wear and tear
on the machine.

General Description

The disclosed method incorporates PTH into the design of existing mold gates without significant changes in the manufacturing process. The presence of PTH in the mold gate improves its overall adhesion to the substrate by creating inter-layer contacts. The copper barrel of the PTH is plated simultaneously with the base copper of the mold gate, ensuring continuity of the coppe...