Reinforced Lead Frame Structure to Reduce Handling Deformation
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Solution Overview
Problem
The backend fabrication process for semiconductor devices often results in lead frame deformation during handling, leading to damage and a reduction in the number of acceptable units per lead frame sheet.
Innovation Solution
Incorporating reinforcement features such as bridge and ribbon features across dam bars between adjacent lead frames, which provide structural support and increase thickness in key areas to resist deformation, along with tie bars that reduce electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If lead frames are made thin to reduce material usage and cost, then manufacturing cost decreases, but the lead frames become more susceptible to deformation during handling
Solution Approach 1:
The patent introduces reinforcement features that extend through the thickness dimension of the lead frame sheet, creating a three-dimensional structure. These features include raised portions and recesses that add vertical dimension to the otherwise planar thin lead frames, providing structural support without increasing lateral material usage.
Solution Approach 2:
The lead frame sheet is formed as a composite structure with varying thickness regions. The base layer provides the thin, low-cost substrate, while added reinforcement features (raised portions, recesses, and varying thickness zones) create a composite structure that combines the benefits of thin material usage with localized structural strength where needed.
2Stability of the object's composition
If reinforcement features are added to prevent deformation, then structural stability improves, but the complexity of the lead frame structure increases
Solution Approach 1:
Rather than uniformly thickening the entire lead frame sheet, the patent applies reinforcement features only in specific locations where structural support is needed. The lead frame maintains its thin profile in non-critical areas while having localized thickness variations and reinforcement features only where deformation would occur during handling and processing.
Solution Approach 2:
The lead frame sheet is segmented into multiple functional zones with different thickness characteristics. These include thin regions for cost efficiency, localized raised portions for structural support, and recesses for specific functional requirements. This segmentation allows each zone to be optimized for its specific purpose without compromising the entire structure.
3Productivity
If the lead frame sheet is handled extensively during fabrication, then productivity increases, but deformation and damage to lead frames increase
Solution Approach 1:
The reinforcement features, including raised portions and varying thickness zones, are built into the lead frame structure before the fabrication process begins. These pre-integrated structural elements act as cushioning support that prevents deformation during subsequent handling, picking, placing, and processing operations throughout the fabrication sequence.
Solution Approach 2:
The lead frame sheet is pre-formed with integrated reinforcement features and structural variations before any handling or assembly operations. This preliminary structuring ensures that the lead frames are deformation-resistant from the outset, enabling extensive handling during fabrication without compromising integrity or requiring rework.
Data Source
AI summary
A lead frame sheet can include a plurality of lead frames and a reinforcement feature. A pair of adjacent lead frames includes an arrangement of opposing leads along adjacent edges thereof, in which the opposing leads are spaced apart from and coupled to each other by an elongated dam bar. The dam bar extends longitudinally along the adjacent edges of the adjacent lead frames. The reinforcement feature extends across the dam bar, in which the leads and the reinforcement feature have a thickness, in a direction orthogonal to a surface of the sheet, which is greater than a thickness of the dam bar.