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Method for a thin, spacerless quadruple stack chip scale package and an underfill material for overhang in molded matrix array packages with multiple dice

IP.com Disclosure Number: IPCOM000007945D
Publication Date: 2002-May-07
Document File: 8 page(s) / 483K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a thin, spacerless quadruple stack chip scale package (TSQS-CSP) and an underfill material for overhang in molded matrix array packages with multiple dice (MMAPx). Benefits include improved reliability and reduced defects.

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Method for a thin, spacerless quadruple stack chip scale package and an underfill material for overhang in molded matrix array packages with multiple dice

Disclosed is a method for a thin, spacerless quadruple stack chip scale package (TSQS-CSP) and an underfill material for overhang in molded matrix array packages with multiple dice (MMAPx). Benefits include improved reliability and reduced defects.

Background

              A trend in IC technology is dice stacking. With the intention of increasing the functionality of the package, two or more dice are stacked within a package. This arrangement brings about many combinations of die sizes. The ideal case is that the bottom die is bigger than the top die on all sides (Figure 1). However, when this is not the case, overhang is produced. Two sides of the bottom die are smaller than the top die (see Figure 2).

              Conventional stacking of two or more dice chip scale packages (CSPs) or ball grid array (BGA) packages is achieved by attaching the second die on top of the first coupled with conventional gold ball bonding. This solution applies to different-size dice, where the bottom die is larger than the top. Where both dice are approximately the same dimensions, a blank silicon spacer is used between the top and bottom dice (see Figure 3). This arrangement, called spacer or sandwich technology, provides wire-loop clearance between the top and bottom dice. This solution is limited by package thickness and die/spacer thickness. A stacked chip scale package (SCSP) with four dice of similar dimensions must have three silicon spacers in between the dice (see Figure 4). The resulting package might not be a practical solution because of increased package thickness. In addition, the package is prone to wire sway and sweep because of the long wires connecting the top die and substrate.

Description

              The disclosed method is comprised of two parts for dice with different height and width dimensions:

§         A thin, spacerless quadruple package (see Figure 5)

§         Underfill material for overhang in MMAPx

TSQS-CSP

              The disclosed method utilizes the following elements to achieve a TSQS-CSP:

§         Stepped or layered substrate. The substrate land pads are in a different plane, step, or layer. This arrangement enables bonding on the different layers, using shorter wires between bond-pad and land-pad connections. The wire length is minimized with less wire consumption and fewer incidents of wire sweep and sway.

§         Cross-die bonding. The 2nd die and 4th dice are die-attached in opposing orientation to the 1st and 3rd dice respectively. The wirebond is on opposite sides, preventing wiring shorts.

              The disclosed method does not require development for the CSP assembly capability but does require substrate redesign.

Underfill material fo...