Ribbed Lead Frame Section Bars for Sag Prevention
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Solution Overview
Problem
The existing lead frames tend to sag downward during semiconductor device assembly and manufacturing, leading to potential contact between adjacent frames when stacked, due to increased integration and metal area reduction, which affects productivity and assembly efficiency.
Innovation Solution
A lead frame design featuring rails at both edges with section bars orthogonal to them, where at least one section bar includes a rib formed through a half blanking process to enhance rigidity and prevent sagging, while maintaining manufacturing process compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of lead frame cell lines increases and lead frame cells are arranged with higher integration, then productivity is improved, but the proportion of metal areas decreases causing the lead frame to sag downward
Solution Approach 1:
The lead frame is divided into multiple independent cell lines with individual support structures. Each cell line includes section bars with ribs that provide localized support, allowing the lead frame to maintain stability even as the number of cell lines increases for higher productivity.
Solution Approach 2:
Ribs are formed on the section bars extending in the width direction (second direction), adding a vertical dimension element to counteract the downward sagging force. This dimensional addition provides structural reinforcement without occupying horizontal space that would reduce metal area proportion.
2Productivity
If more components are mounted on a lead frame, then productivity is improved, but the lead frame sags downward in the vertical direction
Solution Approach 1:
The lead frame structure is segmented into multiple section bars, each reinforced with ribs. This segmentation distributes the weight of mounted components across multiple support points, preventing excessive sagging even when numerous components are mounted on the lead frame.
Solution Approach 2:
Ribs are strategically formed on section bars at locations where support is most needed. This local reinforcement provides enhanced strength and sag resistance at critical areas without requiring a complete increase in overall metal area, allowing more components to be mounted while maintaining structural integrity.
3Stability of the object's composition
If a drawing process is performed to form ribs, then lead frame deformation is reduced, but manufacturing complexity increases
Solution Approach 1:
Ribs are formed on section bars during the initial lead frame manufacturing process rather than as a subsequent separate operation. This preliminary action integrates the reinforcement structure creation into the base manufacturing flow, reducing overall manufacturing complexity while achieving the desired stability.
Solution Approach 2:
The manufacturing process utilizes parameter changes in the forming operation to create ribs with optimal dimensions and orientations. By adjusting forming parameters such as rib height, width, and spacing, the process achieves effective sag prevention while maintaining compatibility with existing manufacturing capabilities.
Data Source
AI summary
A lead frame including rails, section bars, and lead frame cells. The rails are respectively arranged at edges of the lead frame extending in a first direction. The section bars extend between the rails in a second direction and are orthogonal to the rails. The lead frame cells are aligned along the section bars. At least one of the section bars includes a rib extending in the second direction and formed through a half blanking process.