Stacked Semiconductor Device With Overhanging Chip Support
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Solution Overview
Problem
Existing semiconductor devices with overhanging portions face challenges in reliable support during wire bonding and resin sealing, leading to issues like chip cracks and inadequate adhesive filling, particularly with thinner chips.
Innovation Solution
A semiconductor device design featuring a wiring substrate with a recessed portion and connection pads, where a first semiconductor chip is mounted, and a second chip with electrode pads is stacked to project out, with its overhanging portions supported on the substrate, ensuring secure support and reduced thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of semiconductor chips is reduced to increase device density, then the device can be more compact and have higher integration, but the overhanging portion becomes more prone to cracking and warping during wire bonding and resin sealing processes
Solution Approach 1:
The support function is segmented into multiple components: the recessed portion of the substrate provides baseline support, while the adhesive layer selectively reinforces the overhanging portion. This segmentation allows different regions to have different support levels appropriate to their structural needs.
Solution Approach 2:
An adhesive layer is introduced as an intermediary substance between the substrate and the overhanging portion of the upper chip. This adhesive mediator fills the gap and provides additional support to the overhanging region, preventing cracking and warping during wire bonding and resin sealing processes.
2Reliability
If a bonding wire or bump is used as a supporting portion for the overhanging portion, then some support is provided, but sections of the overhanging portion remain unsupported, especially problematic for thinner chips
Solution Approach 1:
The adhesive layer serves multiple functions simultaneously: it provides mechanical support to the overhanging portion, fills the gap between the chip and substrate, and enables proper wire bonding. This multi-functionality eliminates the need for separate support structures like additional bumps or wires.
Solution Approach 2:
Instead of providing support only at discrete points (0D) or along lines (1D) with bumps or wires, the adhesive layer provides continuous areal support (2D) across the entire overhanging region, ensuring complete coverage and support.
3Reliability
If adhesive is used to support the overhanging portion with flip-chip mounting, then support is provided, but if the adhesive protrusion is insufficient, the gap between the chip and substrate cannot be properly filled
Solution Approach 1:
The adhesive layer is designed with controlled thickness parameters that ensure adequate protrusion to fill the gap between the chip and substrate. By optimizing the adhesive layer thickness, the design achieves both proper gap filling and sufficient support for the overhanging portion.
Data Source
AI summary
A semiconductor device comprises the following: a wiring substrate having on one side a recessed section and a plurality of connection pads; a first semiconductor chip mounted in the recessed section; a second semiconductor chip that has a plurality of electrode pads on the surface of at least one end section (in this case, both ends) and that is laminated onto the first semiconductor chip so that at least one end section (in this case, both ends) protrudes from the first semiconductor chip; a plurality of wires that mutually and electrically connect the plurality of connection pads of the wiring substrate and the plurality of electrode pads of the second semiconductor chip. One end section of the second semiconductor chip extends beyond the inner surface of the recessed section and is supported by one side of the wiring substrate.