Vertically Offset Leadframe Strip Design for IC Packaging
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Solution Overview
Problem
The existing leadframe strip configuration for making integrated circuit packages results in significant loss of leadframe copper and mold compound due to the need for mold runners and interior vertical rails, limiting the density of leadframes per unit area and requiring complex singulation processes.
Innovation Solution
A leadframe strip design with integrally connected leadframes arranged in vertically offset columns, eliminating the need for outer dam bars and mold runners, allowing for a denser configuration by interdigitating leads between adjacent columns and using adjustable dam bar structures for pitch correction and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If traditional leadframe strip configuration with mold runners and interior vertical rails is used, then structural support and alignment are provided, but significant loss of leadframe copper and mold compound occurs, limiting leadframe density
Solution Approach 1:
The patent removes mold runners and interior vertical rails from the traditional leadframe strip configuration. By extracting these unnecessary structural elements, the design eliminates significant material waste (leadframe copper and mold compound) while maintaining leadframe structural integrity through alternative support mechanisms built into the leadframe structure itself.
Solution Approach 2:
The patent transitions from a two-dimensional arrangement where leadframes are separated by mold runners and vertical rails, to a three-dimensional configuration where leadframes are vertically offset in columns. This dimensional change allows leadframes to be positioned closer together without requiring traditional support structures, thereby increasing leadframe density per unit area.
2Quantity of substance
If traditional leadframe configuration with outer dam bars is used, then leadframe alignment and support are maintained, but leadframe density per unit area is limited
Solution Approach 1:
The patent eliminates outer dam bars from the traditional leadframe configuration. By removing this external support structure, the design achieves higher leadframe density while maintaining alignment through alternative mechanisms such as interdigitated leads and vertically offset column arrangements that provide structural stability without requiring peripheral dam bars.
Solution Approach 2:
The patent combines the functions of support and alignment into the leadframe structure itself rather than relying on separate dam bar components. The interdigitated leads and vertically offset columns work together to provide both structural support and precise alignment, merging multiple functions into integrated structural features.
3Quantity of substance
If leadframes are arranged in vertically offset columns with interdigitated leads, then leadframe density increases, but complex alignment mechanisms are required
Solution Approach 1:
The vertically offset column arrangement with interdigitated leads creates a self-aligning structure where the geometry of the leads and columns automatically ensures proper positioning. The interdigitated leads of adjacent columns interlock in a way that naturally maintains alignment during molding and singulation, eliminating the need for external alignment mechanisms or complex adjustment procedures.
Data Source
AI summary
A leadframe strip for use in making leaded integrated circuit packages includes a plurality of integrally connected leadframes that each have a die attach pad and first and second dam bars located adjacent to opposite first and second sides of the die attach pad, respectively. A plurality of continuous lead structures extend, uninterrupted by other structure, between opposing ones of the dam bars of horizontally adjacent leadframes. The plurality of integrally connected leadframes are arranged in a plurality of vertical columns, wherein die attach pads in one vertical column are vertically offset from die attach pads in adjacent vertical columns.