Leadframe Design for Semiconductor Package Interposer Elimination
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Solution Overview
Problem
Conventional leadframe-based semiconductor packages require an interposer layer to route connections between semiconductor die bond pads and external leads, leading to increased fabrication time and expense due to electrical shorts caused by lead crossovers in single-layer leadframes.
Innovation Solution
A leadframe design with customized lead patterns and die bond pad positions minimizes the distance between bond pads and leads, allowing direct electrical coupling without crossing leads, eliminating the need for an interposer layer by using copper or copper alloys and forming leads through mechanical stamping or photolithographic techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer leadframe is used to connect die bond pads to external leads, then the device complexity is reduced, but electrical shorts occur due to lead crossovers requiring an interposer layer
Solution Approach 1:
The patent transitions from a single-layer (2D) leadframe to a multi-layer (3D) leadframe structure. The interposer layer is added as a second metal layer that provides vertical routing capability through vias, allowing leads to cross under each other without electrical shorts. This dimensional change enables complex electrical connections while maintaining reliability.
Solution Approach 2:
The interposer layer acts as an intermediary between the die bond pads and the external leads. It provides intermediate connection points and routing paths that facilitate electrical connections without direct lead crossovers on the same layer, thereby preventing electrical shorts while enabling the required connectivity.
2Reliability
If an interposer layer is added to prevent lead crossovers, then electrical reliability is improved, but fabrication time and expense increase
Solution Approach 1:
The patent combines the interposer layer with the leadframe structure itself, making the interposer an integral part of the leadframe rather than a separate component. This merging allows the interposer layer to be formed simultaneously with the leadframe leads through coordinated photolithographic patterning and metal deposition processes, eliminating sequential fabrication steps and reducing overall fabrication time.
Solution Approach 2:
The interposer layer serves multiple functions: it prevents electrical shorts between crossing leads, provides additional connection points for die bond pads, and enables complex routing patterns. By making this single layer perform multiple functions, the patent reduces the need for additional separate components or processing steps, thereby reducing fabrication complexity and time.
3Reliability
If an interposer layer is added to prevent lead crossovers, then electrical reliability is improved, but manufacturing cost increases
Solution Approach 1:
The interposer layer is merged with the leadframe manufacturing process, allowing both to be fabricated simultaneously using the same photolithographic and metal deposition equipment. This integration eliminates the need for separate interposer fabrication and assembly steps, reducing manufacturing complexity and cost while maintaining electrical reliability.
Solution Approach 2:
The patent optimizes the thickness and material composition of the interposer layer to match the leadframe parameters, allowing both to be processed together. By coordinating the fabrication parameters of the interposer with the leadframe, the patent achieves cost-effective manufacturing without compromising electrical connection reliability.
Data Source
AI summary
A semiconductor package is disclosed including a leadframe, memory die and controller die, one or more of which are customized to facilitate electrical connection of the memory and controller die bond pads to the contact pads of the host device via the leadframe. By customizing one or more of the leadframe, memory die and controller die, an interposer layer normally required to connect the die in the semiconductor package with a host device may be omitted.