Pentagonal Cross-Section Lead Frame for Deformation and Burr Control
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Solution Overview
Problem
The existing lead frames for mounting semiconductor chips are prone to deformation due to external forces, which makes reliable connection with the chip difficult, and they also tend to generate burrs during cutting, due to their concave back surface and reduced cross-sectional area.
Innovation Solution
A lead frame with a pentagonal cross-sectional shape having a quadrangular main body and a triangular protrusion on the back surface, where the width of the lower end is smaller than the upper end, is designed to increase strength and prevent deformation, while reducing the cross-sectional area to minimize burr formation during cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the lead is formed by half etching a metal plate to reduce thickness, then the cross-sectional area is reduced, but the lead becomes prone to deformation under external force
Solution Approach 1:
The lead cross-section is designed with an asymmetric shape where the back surface protrudes outward rather than being concave. This asymmetric geometry increases the cross-sectional area and material distribution, thereby enhancing the lead's strength and resistance to deformation while maintaining the thinned profile for other benefits.
Solution Approach 2:
The invention changes the geometric parameters of the lead cross-section by introducing a protrusion on the back surface. This parameter change optimizes the balance between cross-sectional area and strength, allowing the lead to maintain both reduced overall thickness and sufficient structural integrity.
2Device complexity
If the lead has a conventional cross-sectional shape, then the structure is simple, but burrs are generated during cutting
Solution Approach 1:
The asymmetric cross-sectional shape with the back surface protrusion is specifically designed to prevent burr formation during cutting. The geometric configuration optimizes the cutting process by directing material flow and reducing stress concentration at the cut edge, thereby improving manufacturing precision without requiring complex multi-component structures.
Data Source
AI summary
A lead frame includes a frame part, a lead extending inward from the frame part and having a front surface and a back surface, and an external connection terminal formed at a part of the lead in an extension direction and protruding from the back surface of the lead. The lead includes a pentagonal shape in a cross-section where the front surface of the lead faces upward, the pentagonal shape having a quadrangular main body part and a triangular protrusion protruding from a lower surface of the main body part. A width of a lower end of the main body part is smaller than a width of an upper end of the main body part.