3D Stacked QFN Packaging for Higher SMD Integration Density
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Solution Overview
Problem
Conventional quad flat no-lead (QFN) semiconductor packages are limited in available space, restricting the number of components that can be integrated and requiring increased package size to accommodate surface mounted devices (SMDs), due to mismatched lead pitches.
Innovation Solution
Positioning one or more electrical components between the semiconductor die and the QFN leadframe, with wire bonds connecting the die to the leads, allowing for the integration of SMDs without increasing the package size by using recessed leads and die pads for efficient component stacking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional QFN package design is used, then the package structure is simple and manufacturing is easy, but the available space is limited and component integration is restricted
Solution Approach 1:
The patent transitions from a conventional planar arrangement to a three-dimensional stacked architecture. Electrical components are positioned vertically between the semiconductor die and the leadframe, utilizing the Z-dimension to increase component density without expanding the package footprint. This vertical stacking enables integration of additional components while maintaining the compact QFN form factor.
Solution Approach 2:
The patent implements a nested configuration where electrical components are embedded within the vertical space between the die and leadframe. The components are positioned in the available volume, effectively nesting them within the package structure. This nesting approach maximizes space utilization and allows multiple components to coexist in a confined area.
2Quantity of substance
If SMDs are integrated in conventional QFN packages, then component functionality is improved, but the lead pitch mismatch prohibits mounting and increases package size
Solution Approach 1:
The patent introduces an intermediary mounting structure that bridges the leadframe and the electrical components. This intermediate platform provides appropriate pitch dimensions for SMD mounting, acting as a mediator between the QFN leadframe geometry and the SMD component requirements. The intermediary structure enables standard SMD mounting techniques to be applied without modifying the underlying leadframe.
Solution Approach 2:
The patent segments the mounting function from the leadframe structure itself. Instead of requiring the leadframe to directly provide SMD-compatible pitch, the solution divides the system into the leadframe base structure and a separate mounting platform layer. This segmentation allows each component to be optimized independently - the leadframe maintains its compact QFN form while the mounting platform provides appropriate pitch dimensions.
3Quantity of substance
If the package size is increased to accommodate SMDs, then component integration is enabled, but the compact footprint advantage is lost
Solution Approach 1:
The patent resolves this contradiction by exploiting the vertical dimension. Instead of expanding the package area to accommodate additional components, the solution stacks components vertically between the die and leadframe. This dimensional transition allows high component count while preserving the compact footprint characteristic of QFN packages.
Solution Approach 2:
The patent changes the spatial distribution parameter from planar to vertical. By repositioning components from a horizontal arrangement to a vertical stack, the solution increases component capacity without increasing the planar footprint. This parameter change in spatial organization enables density improvement while maintaining compact dimensions.
Data Source
AI summary
One or more embodiments are directed to quad flat no-lead (QFN) semiconductor packages, devices, and methods in which one or more electrical components are positioned between a die pad of a QFN leadframe and a semiconductor die. In one embodiment, a device includes a die pad, a lead that is spaced apart from the die pad, and at least one electrical component that has a first contact on the die pad and a second contact on the lead. A semiconductor die is positioned on the at least one electrical component and is spaced apart from the die pad by the at least one electrical component. The device further includes at least one conductive wire, or wire bond, that electrically couples the at least one lead to the semiconductor die.