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Stack Die Packaging Using a Radiation Cure

IP.com Disclosure Number: IPCOM000103395D
Publication Date: 2005-Mar-17
Document File: 3 page(s) / 100K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses a radiation cure for stack die encapsulation to prevent wire sweep problems resulting in electrical short and void issues that occur during the mold process. Benefits include reducing curing times and lowering curing costs.

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Stack Die Packaging Using a Radiation Cure

Disclosed is a method that uses a radiation cure for stack die encapsulation to prevent wire sweep problems resulting in electrical short and void issues that occur during the mold process. Benefits include reducing curing times and lowering curing costs.

Background

Wire deformation (i.e. wire sweep) is due to the drag force on the wire from the mold flow. The resin transfer molding (RTM) is the current molding method (see Figure 1). As the package height is increased with multiple die stacking, the bond wire length is also increased, and the incidences of circuit shorting increase; this is one of the leading causes of low yield in the assembly process.

Void generation is another issue during the RTM process, and there are two types of voids generated: filling voids and density voids. Filling voids are air bubbles trapped in the mold, due to the mold geometry and flow patterns in the filling stage. Density voids are caused by resin shrinkage, especially when polymerization occurs in an improper order.  These voids are thermal and mechanical defects, increasing thermal resistance and serving as a crack initiation point.

General Description

The disclosed method uses a radiation cure of thermoset resin, which is processed in a liquid state before polymerization. Radiation curing uses either high-energy electrons (i.e. e-beam) or ultraviolet (UV) to initiate the polymerization and cross-linking of the thermoset resin
(see Figure 2). It is a non-thermal curing process t...