Multi-Chip QFN Packaging Structure for High Density Integration
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Solution Overview
Problem
Current multi-chip microelectronic packaging technologies face challenges in increasing packaging density and efficiency due to increased transmission distances and decreased density from stacking multiple packages, which often require reconfiguration of leadframes to accommodate additional dies and maintain electrical connectivity.
Innovation Solution
The proposed solution involves a multi-chip QFN packaging design where a first die is wire-bonded to a leadframe, and a second die is mounted on the first die or flip-chip mounted on the leadframe, with both dies encapsulated in a mold compound, and electrically interconnected using conductive bumps, allowing for a back-to-back or flip-chip configuration that maintains compactness and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple packages are stacked to meet system performance demands, then system functionality is improved, but transmission distance increases and packaging density decreases
Solution Approach 1:
The patent implements nesting by placing one die inside another die's package cavity. Specifically, a first die is mounted on a leadframe with its active side facing upward, then a second die is mounted on top of the first die such that the second die is partially or fully enclosed within the package structure of the first die. This nested arrangement allows multiple functional units to coexist in a compact vertical stack, improving packaging density while maintaining short transmission distances through the leadframe's conductive paths.
Solution Approach 2:
The patent transitions from planar packaging to three-dimensional stacking by utilizing the vertical dimension. Multiple dies are arranged in a vertical stack along the z-axis, with each die mounted on successive levels of the leadframe structure. This dimensional change enables higher packaging density without increasing the footprint area, while the leadframe provides direct electrical interconnection between stacked dies, maintaining short transmission paths.
2Adaptability or versatility
If multiple packages are stacked to enhance system performance, then system functionality is improved, but transmission distance increases
Solution Approach 1:
By nesting dies within each other's package structures, the patent minimizes the vertical distance between stacked dies. The leadframe extends through the nested structure, providing direct electrical pathways that bypass long transmission routes. This nesting approach ensures that even though multiple functional units are integrated, the electrical transmission distance remains short due to the direct conductive connections through the leadframe.
Solution Approach 2:
The leadframe serves as an intermediary structure that provides direct electrical interconnection between stacked dies. Instead of relying on long external traces or complex inter-package connections, the leadframe's conductive elements create short, direct pathways for signal transmission between dies mounted at different vertical levels, thereby minimizing transmission distance while enabling multi-die functionality.
3Adaptability or versatility
If leadframes are reconfigured to accommodate additional dies, then multi-chip integration is improved, but manufacturing complexity increases
Solution Approach 1:
The leadframe is designed with universal, reusable structures that can accommodate multiple dies in standardized configurations. Rather than custom-reconfiguring leadframes for each multi-chip integration, the patent employs leadframes with repeated conductive elements and mounting structures that can consistently support stacked dies. This universal design simplifies manufacturing by allowing the same leadframe architecture to be used across different multi-chip packages, reducing complexity while maintaining integration capability.
Data Source
AI summary
Multi-chip quad flat no-lead (QFN) packages and methods for making the same are disclosed. A multi-chip package may include a first die including a plurality of first bond pads, wherein selected first bond pads are wire-bonded to a first side of a leadframe, and a second die mounted on the first die and including a plurality of second bond pads, wherein selected second bond pads are wire-bonded to a second side, opposite the first side, of the leadframe. Another package may include a first die including a plurality of first bond pads, wherein selected first bond pads are wire-bonded to a first side of a leadframe, and a second die flip-chip mounted on a second side of the leadframe and including a plurality of second bond pads, wherein selected second bond pads are bonded to the second side of the leadframe. Other embodiments are also described.