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Stacked Mixed-Technology SCSP with Flat Ribbon Second Level Interconnect

IP.com Disclosure Number: IPCOM000126994D
Publication Date: 2005-Aug-16
Document File: 4 page(s) / 242K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a mixed-technology SCSP that uses a substrate with a base layer of C4 land pads for the flip chip, and flat ribbon-type, second-level interconnects (SLI). Benefits include reduced package thickness, reduced process costs, and higher assembly and test yields.

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Stacked Mixed-Technology SCSP with Flat Ribbon Second Level Interconnect

Disclosed is a method for a mixed-technology SCSP that uses a substrate with a base layer of C4 land pads for the flip chip, and flat ribbon-type, second-level interconnects (SLI). Benefits include reduced package thickness, reduced process costs, and higher assembly and test yields.

Background

Currently, there are issues associated with stacking multiple devices in mixed-technology SCSPs, especially devices with similar or identical sizes. It is difficult to accommodate the static device bond pad layout within the interconnect process. It is also difficult to stack multiple mixed-technology SCSP packages.

Conventional SCSPs use spacers to offset the upper devices in the z-direction, allowing the lower devices to be wire bonded to the substrate. Also, redistribution layers (RDLs) are used to reroute device bond pad locations to a different pattern that is more suited to device stacking and wire bonding. Mixed-technology SCSPs are usually not package stacked.  Folded flexible substrates are used for stacking conventional SCSPs where the signals from the top package are routed through the traces in the fold flap. See Figure 1b.

General Description

The two key components of the disclosed method are the substrate with the built up layers of peripheral lead fingers, and the ribbon SLI. Current substrate manufacturing is sufficient to create the substrate and the ribbon SLI. The ribbon SLI, in its simplest form, can be a flexible material to which a conductive foil is glued before the patterning of the foil is completed by lithography or etching. The final pattern on the carrier is the two-dimensional routing pattern used to connect specific device bond pads to the desired lead fingers on the substrate.

For package assembly, the disclosed method uses current processes and tools to manufacture SCSPs, except the interconnect process for the ribbon SLI. In its simplest form, one end of the conductive traces contacts the device bond pads and the other end to the substrate lead fingers; the conductive traces are secured to the bond pad and lead finger with a conductive adhesive, then released from the pattern carrier. This process can be developed as a modified TAB- or lead-bonding process. The die at...