Isolated Inner Lead Rerouting in Semiconductor Leadframes
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Solution Overview
Problem
Existing leadframe technologies restrict pin assignment rerouting and increase packaging complexity due to fixed lead sequences, leading to higher costs and risks of wire bonding issues like height differences and displacement.
Innovation Solution
A method for forming isolated inner leads within a leadframe, allowing for pin assignment rerouting without additional internal components, using a leadframe design with defined molding and die-attaching areas, insulating tapes, and a connecting block to electrically isolate inner leads, enabling redistribution of electrical paths without increasing package height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If leads are formed from the same layer of leadframe with fixed sequence, then manufacturing is simple, but pin assignment rerouting is not possible
Solution Approach 1:
The leadframe is segmented into multiple independent metal layers, with each layer containing specific leads for different functions. The first metal layer contains outer leads for external connections, while the second metal layer contains inner leads for internal connections. This layering enables flexible pin assignment rerouting by selectively connecting different layers at bonding pads without increasing overall structural complexity.
Solution Approach 2:
The invention transitions from a two-dimensional single-layer leadframe to a three-dimensional multi-layer structure. By adding the vertical dimension with multiple stacked metal layers, the patent enables pin assignment rerouting capabilities that were impossible in the planar single-layer configuration, while maintaining manufacturing feasibility through standard multi-layer fabrication processes.
2Adaptability or versatility
If extra internal redistributing components are disposed on leadframe, then pin assignment rerouting is enabled, but packaging complexity increases
Solution Approach 1:
The patent merges the leadframe structure with the internal redistributing function by integrating multiple metal layers directly into the leadframe itself. The inner leads on the second metal layer serve dual purposes: providing structural support like traditional leads and enabling pin assignment rerouting through controlled connections at bonding pads. This eliminates the need for separate external redistributing components and simplifies packaging processes.
Solution Approach 2:
The multi-layer metal structure serves multiple functions simultaneously: it provides mechanical support, establishes electrical connections, enables pin assignment rerouting, and facilitates wire bonding. The inner leads on the second metal layer can be configured to connect to specific outer leads or remain isolated, providing universal adaptability for different pin assignment requirements without requiring additional specialized components.
Data Source
AI summary
A method for forming an isolated inner lead from a leadframe is revealed. The leadframe primarily comprises a plurality of leads, the isolated inner lead, and an external lead. Each lead has an inner portion having a finger. The isolated inner lead having two fingers is completely formed inside a molding area and is made of the same metal leadframe as the leads. One finger of the isolated inner lead and the fingers of the leads are linearly arranged. The other finger of the isolated inner lead is adjacent to a finger of the external lead. At least one of the inner portions divides the isolated inner lead from the external lead. The isolated inner lead is integrally connected to an adjacent one of the inner portions by a connecting block. A tape-attaching step is performed to mechanically connect the isolated inner lead where two insulating tapes are attached in a manner that the connecting block can be removed. Therefore, the isolated inner lead is electrically isolated from the leads and can be mechanically fixed to replace extra redistributing components during semiconductor packaging processes.