Stacked Semiconductor Underfill Pedestal for Side Face Sealing
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Solution Overview
Problem
In semiconductor devices with stacked chips, where the second chip is larger than the first, it is difficult to ensure reliable coverage of the second chip's side face with underfill resin, leading to potential moisture ingress and reliability issues.
Innovation Solution
A semiconductor device design that includes a pedestal portion of underfill resin around the first chip, allowing the second underfill resin to cover the upper face of the pedestal and the side face of the larger second chip, ensuring complete sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the second semiconductor chip is made larger than the first semiconductor chip to increase mounting density, then the mounting density is improved, but the underfill resin cannot cover the side face of the second semiconductor chip, leading to poor reliability
Solution Approach 1:
The invention transitions from a single-layer underfill structure to a multi-layer underfill structure by adding a second underfill resin on top of the first underfill resin. This dimensional change in the underfill arrangement enables complete coverage of the second semiconductor chip's side face, solving the sealing reliability issue while maintaining the high mounting density achieved through chip stacking
Solution Approach 2:
The first underfill resin is applied and cured before mounting the second semiconductor chip, creating a preliminary sealing layer and pedestal portion. This preliminary action prepares the structure to receive and support the second underfill resin, ensuring that when the second chip is mounted, the side face can be fully covered without compromising reliability
2Reliability
If underfill resin is filled between stacked semiconductor chips, then moisture ingress is prevented, but when the upper chip is larger than the lower chip, the side face of the upper chip cannot be covered, reducing sealing effectiveness
Solution Approach 1:
The underfill resin is segmented into two distinct layers: the first underfill resin filled between the wiring substrate and the first semiconductor chip, and the second underfill resin filled between the first and second semiconductor chips. This segmentation allows each layer to perform its specific sealing function independently, ensuring complete coverage and effective moisture protection
Solution Approach 2:
The first underfill resin acts as an intermediary structure with a pedestal portion that supports and positions the second underfill resin. This intermediary arrangement enables the second underfill resin to properly cover the side face of the larger second semiconductor chip, achieving precise sealing coverage that neither layer could accomplish alone
Data Source
AI summary
A semiconductor device includes a wiring substrate, a first semiconductor chip flip-chip connected to the wiring substrate, a first underfill resin filled between the wiring substrate and the first semiconductor chip, the first underfill resin including a pedestal portion arranged in a periphery of the first semiconductor chip, a second semiconductor chip flip-chip connected to the first semiconductor chip, and being larger in area than the first semiconductor chip, and a second underfill resin filled between the first semiconductor chip and the second semiconductor chip, the second underfill resin covering an upper face of the pedestal portion of the first underfill resin and a side face of the second semiconductor chip.