Semiconductor Lead Frame Tie Bar Segmentation for Terminal Thickness Uniformity
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Solution Overview
Problem
Conventional semiconductor devices face challenges in high-power applications due to unequal thicknesses of power-side and control-side terminals, leading to uneven stress distribution and solder fusion when mounted on a substrate, as increasing terminal pitch requires larger connection widths and thicknesses, making uniform mounting difficult.
Innovation Solution
A method for manufacturing semiconductor devices involving a lead frame with tie bar portions connecting terminals, where the terminals are encapsulated in mold resin with only the necessary tie bar portions exposed, allowing for equal thickness settings and improved mounting on a substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal pitch of the power-side terminal is increased to secure insulation distance and spatial distance in high-power applications, then the insulation performance is improved, but the connection width and thickness of the power-side terminal must be increased for machining reasons, making it impossible to set the thickness equal to the control-side terminal, which worsens the uniformity of stress distribution and solder fusion during mounting
Solution Approach 1:
The invention segments the tie bar portions into two distinct types: those connecting power-side terminals (first tie bar portions) and those connecting control-side terminals (second tie bar portions). This segmentation allows each type to have optimized dimensions suitable for its function, with the first tie bar portions having larger dimensions for high-power carrying capacity and the second tie bar portions having smaller dimensions for control signal transmission, thereby resolving the contradiction between insulation requirements and manufacturing uniformity
Solution Approach 2:
The invention applies local quality by giving different tie bar portions different dimensions based on their specific functional requirements. Power-side tie bar portions are designed with larger width and thickness to handle high current and provide mechanical strength, while control-side tie bar portions use smaller dimensions appropriate for low-power signals. This localized optimization allows each region of the lead frame to have the precise characteristics needed for its operation
2Stability of the object's composition
If the connection width of the frame from the die pad to the tie bar portion is increased to reduce flutters of the die pad, then the mechanical stability is improved, but the thickness of the power-side terminal becomes larger due to machining constraints, worsening the ability to achieve uniform thickness with control-side terminals
Solution Approach 1:
The invention segments the connection structure into die pad connection portions and tie bar portions, allowing each to be independently optimized. The die pad connection portions can be designed with sufficient width to reduce flutters and provide mechanical stability, while the tie bar portions are segmented into power-side and control-side types with appropriately differentiated thicknesses, resolving the contradiction between mechanical stability and manufacturing uniformity
Solution Approach 2:
The invention applies local quality by optimizing the connection width and thickness locally for each functional region. The die pad connection portions have sufficient width for mechanical stability, while the resulting tie bar portions have locally optimized dimensions - larger for power-side connections and smaller for control-side connections - enabling uniform terminal thickness to be achieved during mounting
Data Source
AI summary
A method for manufacturing a semiconductor device according to the present invention includes the steps of (a) preparing a lead frame including a power chip die pad to which two terminals are connected, a control element die pad to which one terminal is connected, and tie bar portions connecting between a plurality of terminals including the two terminals, (b) placing a power chip and a free wheel diode on the power chip die pad and placing ICs on the control element die pad, (c) encapsulating in a mold resin to allow the tie bar portions to be exposed outside and a plurality of terminals including the two terminals and the one terminal to protrude outward, and (d) removing the tie bar portions other than the tie bar portions connecting the two terminals.