Lead Frame Strip Trenches Guide Molding Material for Electrical Isolation
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Solution Overview
Problem
In lead frame strip processing, tie bars formed from the same material as die paddles cause electrical shorts, complicating electrical testing and requiring electrical isolation for applications like DSO packages, and existing methods struggle with partial plating and electrical charge processes.
Innovation Solution
The method involves forming molding compound channels in the periphery structure of lead frame strips to guide liquefied molding material, which encapsulates semiconductor dies and forms molding extensions that provide physical support without electrical connections, allowing for strip-level testing and eliminating the need for tie bars.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If tie bars are used to physically support semiconductor dies during processing, then mechanical support is provided, but electrical shorts occur between die paddles and lead frame strip
Solution Approach 1:
The patent removes tie bars from the lead frame structure entirely. Instead, the molding compound itself provides mechanical support to the semiconductor dies during processing. This extraction of the tie bar component eliminates the electrical shorting problem while maintaining mechanical support through the molding compound and groove structure.
Solution Approach 2:
The patent introduces molding compound grooves as an intermediary structure between the die paddle and the lead frame strip. These grooves receive molding compound that acts as a mediator, providing mechanical support without creating electrical connections. The groove structure guides the molding material to specific locations where it can support the die without contacting conductive elements.
2Stability of the object's composition
If tie bars are used for physical support, then processing stability is improved, but electrical isolation requirements complicate testing and processing
Solution Approach 1:
The patent extracts the electrical isolation function from the mechanical support structure. By removing tie bars and using only molding compound for support, the system eliminates the need for electrical isolation measures during testing and processing. The molding compound naturally provides both mechanical support and electrical isolation without requiring additional complex procedures.
Solution Approach 2:
The molding compound serves multiple functions simultaneously: it provides mechanical support to the semiconductor dies, provides electrical isolation between conductive elements, and enables direct electrical testing without additional isolation steps. This multi-functionality simplifies the overall processing system by combining support and isolation functions in a single material.
3Ease of manufacture
If conventional lead frame structures are used, then manufacturing is simple, but corrosion and delamination risks increase
Solution Approach 1:
The patent adds a vertical dimension to the support structure by creating grooves that extend downward from the surface of the lead frame strip. These grooves receive molding compound that wraps around and under the die paddle, creating a three-dimensional support structure that enhances mechanical bonding and reduces delamination risk while maintaining manufacturing simplicity.
Solution Approach 2:
The patent creates a composite structure combining the lead frame strip (metal), molding compound (polymer), and semiconductor die. The molding compound acts as a bonding layer between the metal lead frame and the semiconductor die, providing corrosion resistance and preventing delamination through strong adhesive bonding, while the groove structure enhances this composite bonding.
Data Source
AI summary
A unit lead frame includes a periphery structure, a die paddle inside of the periphery structure, a plurality of leads extending between the periphery structure and the die paddle, and trenches or grooves extending from an outer surface of the periphery structure and configured to guide liquefied molding material onto the periphery structure along sidewalls of the trenches or grooves.