Routing Substrate in Lead Frame QFN Package
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Solution Overview
Problem
Conventional Quad Flat No-lead (QFN) packages are inflexible and struggle to accommodate IC dies with non-conventional die-pad configurations, such as elongated rectangular or complex pad arrangements, leading to bond wire routing issues like interference and insufficient spacing.
Innovation Solution
A semiconductor device package design that includes a lead frame with a routing substrate having inner and outer bond pads, allowing for interconnections between the IC die and lead frame through multiple steps, which improves bond wire spacing and eliminates interference by using a routing substrate with inner and outer bond pads arranged in parallel rows and a square pattern respectively, independent of the lead frame's arrangement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional QFN package with leads on all four sides is used, then the package structure is simple and manufacturing is straightforward, but it cannot accommodate IC dies with non-conventional die-pad configurations such as elongated rectangular or complex pad arrangements
Solution Approach 1:
A routing substrate is introduced as an intermediary component between the IC die and the lead frame. The routing substrate features inner bond pads that can be arranged in various configurations to match different IC die pad layouts, and outer bond pads that connect to the lead frame leads. This intermediary layer enables flexible accommodation of elongated rectangular, complex, or non-conventional die-pad configurations without requiring changes to the standard lead frame structure, thus resolving the contradiction between adaptability and device complexity.
2Reliability
If bond wires are routed directly between die pads and lead frame leads in a conventional QFN package, then the electrical path is short, but bond wires from corner die pads cannot be spaced sufficiently apart and will interfere with one another
Solution Approach 1:
The direct bond wire connection between the IC die and lead frame is segmented into two separate connection stages. First, bond wires connect the IC die die pads to the inner bond pads on the routing substrate. Second, additional bond wires or interconnections on the routing substrate connect the inner bond pads to the outer bond pads, which then connect to the lead frame leads. This segmentation allows sufficient spacing between bond wires, particularly for corner die pads, eliminating interference while managing the electrical path length through optimized routing on the substrate.
3Adaptability or versatility
If the lead frame and IC die pad arrangements are made independent of each other, then the package can accommodate various IC die configurations, but the bond wire routing becomes more complex
Solution Approach 1:
The routing substrate serves as a mediator that decouples the lead frame lead arrangement from the IC die pad arrangement. The inner bond pads on the routing substrate are configured to match the IC die pad layout (e.g., elongated rectangular patterns), while the outer bond pads are arranged to match the lead frame lead pattern. This intermediary configuration allows independent optimization of each component's arrangement without directly coupling their complexities, as the routing substrate absorbs and manages the routing complexity through its layered pad structure.
Data Source
AI summary
A semiconductor device including a lead frame, a routing substrate disposed within the lead frame, and an active component mounted on the routing substrate. The active component has a plurality of die pads. The routing substrate includes a set of first bond pads, a set of second bond pads, and interconnections, where each interconnection provides an electrical connection between a first bond pad and a corresponding second bond pad. The semiconductor device further includes electrical couplings between one or more of die pads of the active component and corresponding first bond pads of the routing substrate, as well as electrical couplings between leads of the lead frame and respective second bond pads of the routing substrate.