Semiconductor Lead Frame Positioning via Wire Member and Solder Slits
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Solution Overview
Problem
Conventional semiconductor devices face challenges in accurately positioning lead frames and solder layers on insulating substrates, leading to unstable connections and reduced reliability due to thermal stress and uneven solder thickness, especially during the downsizing of semiconductor devices.
Innovation Solution
A semiconductor device design that incorporates a positioning wire member and a lead frame with openings to facilitate precise positioning of the lead frame and solder layers, allowing for efficient heat dissipation and reliable connections without the need for a conventional positioning frame body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder layers are used to mount electronic components on the metal layer, then electrical connection is achieved, but the solder layers shift toward the periphery and spread to the end of the metal layer or other electronic components
Solution Approach 1:
The patent introduces positioning protrusions on the metal layer and corresponding positioning grooves on the solder layer before the soldering process. This preliminary positioning structure ensures that the solder layer is correctly positioned on the metal layer prior to melting, preventing peripheral shifting and spreading during the soldering process.
Solution Approach 2:
The patent uses positioning protrusions and positioning grooves as intermediary structures between the metal layer and the solder layer. These intermediary features act as mechanical guides that constrain the solder layer's position during mounting, ensuring accurate alignment and preventing unwanted movement toward the periphery.
2Ease of manufacture
If the solder layers spread toward the end of the metal layer, then mounting is simplified, but the insulating substrate near the end is exposed to large stress causing cracks on the periphery of each solder layer
Solution Approach 1:
The positioning protrusions and grooves are designed in advance to define the exact boundary where the solder layer should terminate. This preliminary positioning prevents the solder layer from spreading toward the end of the metal layer during mounting, thereby avoiding stress concentration and crack formation on the insulating substrate periphery.
Solution Approach 2:
The positioning structure acts as a preventive measure against solder layer spreading. By providing mechanical constraints before the soldering process, the system preemptively counteracts the tendency of solder to spread toward the periphery, eliminating the root cause of stress-induced cracking.
3Manufacturing precision
If a conventional positioning frame body is used to position the lead frame, then positioning is possible, but the device complexity increases and positioning accuracy is insufficient for downsized devices
Solution Approach 1:
The patent extracts the positioning function from a separate positioning frame body and integrates it directly into the lead frame structure through positioning protrusions and grooves. This integration eliminates the need for a dedicated positioning frame body, reducing device complexity while maintaining positioning accuracy even in downsized devices.
Solution Approach 2:
The positioning features (protrusions and grooves) are merged into the lead frame and solder layer structures themselves. This merging of positioning functionality into the existing components eliminates the need for separate positioning mechanisms, thereby reducing overall device complexity while ensuring accurate lead frame positioning.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables reliable and efficient assembly of semiconductor devices with improved heat release and extended shelf life of solder joints, addressing the issues of thermal stress and positioning accuracy.
Implementation Method 1
joining the lead frame to the electronic components or the conductive pattern via the solder layers
Implementation Method 2
the solder layers are likely to shift toward the periphery on the metal layer
Implementation Method 3
the lead frame itself can function to release the heat of the semiconductor chips to the outside
Data Source
Figure 1(A)~1(B)
Figure 2
Figure 3
AI summary
Provided is a semiconductor device of improved reliability and ease of assembly associated with the downsizing thereof, in which a long shelf life of a solder joining a lead frame having a large current capacity and efficient release of heat from the lead frame can be achieved. In the semiconductor device, electronic components (23, 24) on an insulating substrate formed with a metal layer configuring a conductive pattern (12) are electrically connected to each other by a rectangular lead frame (22). In so doing, the lead frame (22) can correctly be positioned by inserting a wire member (27), which is disposed so as to bridge between the electronic components (23, 24), into an opening (21) formed to penetrate through the lead frame (22). Solder plates (28, 29) are sandwiched, respectively, between the electrode surfaces of the electronic components (23, 24) and joints (22a, 22b) of the lead frame (22), and are melted in a subsequent reflow step. The solder plates (28, 29) are provided with slits (28s, 29s) that are sized corresponding to the width of the opening (21) of the lead frame (22).