Multilayer Package Substrate Layout for QFN Stress Distribution
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Solution Overview
Problem
Conventional Quad Flat No-lead (QFN) package structures are prone to defects and breakage due to lack of support from metal layers, leading to poor reliability and electrical performance.
Innovation Solution
A substrate with sequentially stacked electrically interconnected metal layers and dielectric layers, featuring a low-side power connection region where metal strips extend in different directions, ensuring good stress distribution and high current conduction capability, reducing parasitic resistance and inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional QFN package structure uses only plastic encapsulation material to support portions between lead terminals, then device complexity is reduced, but reliability deteriorates due to extreme proneness to defect formation and breakage under stress
Solution Approach 1:
The patent divides the substrate into multiple metal layers (first metal layer, second metal layer, third metal layer) with dielectric layers interspersed between them. This segmentation provides multiple support levels and stress distribution paths, preventing the single-point failure mode of conventional plastic-only support structures.
Solution Approach 2:
The patent employs a composite structure combining multiple metal materials (copper, aluminum, or aluminum alloy) with dielectric materials. This composite approach creates a multi-functional substrate that simultaneously provides mechanical support, electrical conduction, and stress distribution, overcoming the limitations of single-material conventional packages.
2Manufacturing precision
If metal strips in all metal layers extend in the same direction, then manufacturing precision is simplified, but reliability deteriorates due to poor stress distribution and folding risk
Solution Approach 1:
The patent introduces asymmetric orientation of metal strips in different metal layers. Specifically, metal strips in the first metal layer extend in a first direction, while metal strips in the second metal layer extend in a second direction that is not parallel to the first direction. This asymmetric arrangement creates a cross-support effect that distributes stress more uniformly across the substrate, preventing folding and breakage while maintaining manufacturing feasibility.
3Device complexity
If conventional QFN package uses single-layer metal structure, then device complexity is reduced, but electrical performance deteriorates due to high parasitic resistance and inductance
Solution Approach 1:
The patent transitions from a single-layer metal structure to a multi-layer metal structure stacked in the vertical dimension. By adding multiple metal layers (first, second, and third metal layers) connected through conductive vias, the patent creates three-dimensional current paths that reduce parasitic resistance and inductance, thereby improving electrical performance without significantly increasing overall device footprint.
Data Source
AI summary
A substrate is disclosed, the substrate includes a plurality of electrically interconnected metal layers sequentially stacked from the top downward and dielectric layers interposed between the metal layers. The substrate has a low-side power connection region where metal strips in at least one of the metal layers extend in a direction different from a direction of extension of metal strips in another one of the metal layers extend. This enables a package structure incorporating the substrate to have a good stress distribution, which guarantees reliability required by long-term use. Also provided is a package structure including the substrate and a semiconductor die flipped and mounted on the substrate.