Lead Frame Projection Portions Prevent Ground Ring Scratches
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Solution Overview
Problem
In the manufacturing of lead frames with a common wiring portion around a die pad, existing methods face challenges in cutting off leads without causing scratches or twists, which affects the reliability of wire bonding connections.
Innovation Solution
The introduction of projection portions on the side portions of the common wiring portion, which are pressed partially by the die during cutting, prevents direct contact with the main body of the common wiring portion, thereby avoiding scratches and twists, ensuring reliable wire bonding connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the ground ring is pressed tightly by the pressing member to cut off inner leads, then the inner leads can be cut off satisfactorily without twist, but the surface of the ground ring is easily scratched by the pressing member and supporting member
Solution Approach 1:
The pressing member is divided into two functional parts: a pressing portion that contacts the inner leads for cutting, and a non-pressing portion that is positioned away from the ground ring surface. This segmentation allows the pressing force to be applied precisely where needed (on the inner leads) while avoiding contact with the ground ring surface, thus preventing scratches while maintaining cutting precision.
Solution Approach 2:
The pressing member is designed with localized pressing capability - the pressing portion has the necessary hardness and geometry to cut the inner leads effectively, while the non-pressing portion has a different geometry that prevents contact with the ground ring. This local differentiation of the pressing member's properties allows it to perform the cutting function without causing harmful scratches on the ground ring surface.
2Object-affected harmful factors
If the ground ring is pressed loosely by the pressing member, then the surface of the ground ring is protected from scratches, but the ground ring becomes inclined and twists occur during cutting
Solution Approach 1:
The pressing member is segmented into a pressing portion positioned over the inner leads and a non-pressing portion positioned away from the ground ring. This segmentation enables the pressing portion to provide sufficient downward force to prevent ground ring inclination and twist during cutting, while the non-pressing portion ensures the ground ring surface remains free from scratches.
Solution Approach 2:
The pressing portion acts as an intermediary that transmits the cutting force to the inner leads without directly contacting the ground ring surface. By positioning the pressing portion over the inner leads and using it as the sole contact point for force application, the system achieves both adequate pressing force (preventing inclination) and surface protection (no scratches from the supporting member).
Data Source
AI summary
In the lead frame of the present invention, a common wiring portion (ground ring) is arranged around a die pad at a predetermined interval to be connected partially to the die pad, projection portions projected toward the die pad side are provided to side portions of the common wiring portion, a plurality of leads are provided away from the common wiring portion to extend outward from a periphery of the common wiring portion, and the projection portions of the common wiring portion are pressed partially by the die upon cutting off the leads from the common wiring portion by a die.