Channel-Shaped Leadframe Tie Bars for Stable Semiconductor Singulation
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Solution Overview
Problem
Current semiconductor device manufacturing processes face issues with mechanical cutting during singulation, which induces stresses that can lead to premature failure due to uniform tie bars causing leadframe/mold detachment and increased risk of die pad tilt.
Innovation Solution
Implementing tie bars with a channel-shaped (U-shaped) cross-section at their median part, achieved through coining or etching, which provides higher stiffness and easier cutting during singulation while maintaining stability and reducing stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform rectangular tie bars with constant thickness are used, then the leadframe structure is simple to manufacture, but mechanical cutting during singulation induces stresses that cause leadframe/mold detachment and die pad tilt
Solution Approach 1:
The tie bar cross-section is modified locally at the median part (singulation region) to have a channel-shaped geometry with reduced thickness, while maintaining constant thickness in other regions. This local modification reduces cutting stresses during singulation without compromising the overall structural integrity and support function of the tie bar throughout its length.
Solution Approach 2:
The tie bar is segmented into different functional zones: regions with constant thickness that provide structural support, and a median region with reduced thickness that facilitates low-stress cutting. This segmentation allows each zone to perform its specific function optimally.
2Ease of manufacture
If tie bar thickness is reduced to facilitate cutting, then singulation stresses are reduced, but the risk of die pad tilt during assembly increases
Solution Approach 1:
The tie bar thickness is locally reduced only at the median part where cutting occurs, while maintaining full thickness in the regions that support the die pads. This ensures that die pad support stability is preserved while facilitating easier cutting at the designated singulation location.
Solution Approach 2:
The tie bar structure is divided into support zones (full thickness) and cutting zones (reduced thickness), allowing the support function and cutting function to be optimized independently without compromising either die pad stability or singulation ease.
Data Source
Figure 1~3
Figure 4~6
AI summary
A method of manufacturing semiconductor devices comprises: providing a semiconductor die mounting substrate such as a pre-molded leadframe (12) comprising a plurality of die pads (12A) having opposed first and second surfaces as well as tie bars (20) projecting therefrom, mounting semiconductor dice (14) at the first surface of die pads in the plurality of die pads (12A), and molding encapsulation material onto the semiconductor dice (14) mounted at the first surface of the die pads (12A). A plurality of semiconductor devices is thus produced, with the semiconductor devices (10) in the plurality mutually coupled via the tie bars (20). The tie bars (20) are cut transverse to their longitudinal direction (X20) at an intermediate singulation location to singulate the semiconductor devices into individual semiconductor devices. The tie bars (20) have a hollowed-out portion (20A) with a channel-shaped cross-sectional profile at the intermediate singulation location. Easier-to-cut tie bars (20) can be provided without impairing their stiffness in comparison with tie bars having full rectangular/square cross-sectional shapes.