Stack Die Package Flip Chip Lead Frame
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Solution Overview
Problem
Conventional die packages for DC-DC power supplies face limitations in die size due to wire bonding and soldering processes, affecting drain-to-source resistance and current handling, and incur high assembly costs and reliability issues.
Innovation Solution
The implementation of a stack die package with flip chip technology on a lead frame, eliminating wire bonding and using clips for electrical connections, which allows for larger die sizes and reduced assembly costs by simplifying the design and eliminating the need for silver plating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If wire bonding is used in conventional die packages, then electrical connections can be established, but the die size is limited and assembly cost increases
Solution Approach 1:
The patent extracts and eliminates the wire bonding process from the packaging structure. Instead of using wire bonds to connect the die to the lead frame, the invention uses direct soldering of the die pads to the lead frame, removing the intermediate wire bonding step and enabling larger die sizes without the constraints of wire bonding.
Solution Approach 2:
The patent replaces the mechanical wire bonding system with a direct electrical and mechanical connection through soldering. This substitution eliminates the need for wire bonding equipment and processes, simplifying the overall device structure and enabling larger die dimensions.
2Reliability
If clips are soldered in stack die packages, then electrical connections are established, but wire bond pad surfaces and lead posts become contaminated
Solution Approach 1:
The patent extracts and removes the clips from the packaging structure entirely. Instead of using clips that require soldering and cause contamination, the invention employs a direct soldering approach where the die pads are soldered directly to the lead frame, eliminating the source of contamination while maintaining reliable electrical connections.
Solution Approach 2:
The patent eliminates the clip as an intermediary component between the die and lead frame. By directly soldering the die pads to the lead frame, the invention removes the intermediate element that causes contamination, achieving both reliability and cleanliness.
3Ease of manufacture
If silver plating is applied on the lead frame for wire bonding, then wire bonding can be performed, but lead frame cost increases
Solution Approach 1:
The patent extracts and eliminates the silver plating process from the lead frame manufacturing. By removing wire bonding from the process and using direct soldering instead, the invention eliminates the need for silver plating material, reducing costs while maintaining ease of manufacture through the simplified soldering process.
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 enhances the current handling capability, reduces assembly costs, and improves the reliability of the package by providing a larger contact area and eliminating wire bonding, thus addressing the limitations of conventional packages.
Implementation Method 1
A molding material covers the first die, second die, and clip while a portion of an upper surface of the clip is free of the molding material
Data Source
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Figure 6
AI summary
In one embodiment, a stack die package can include a lead frame and a first die including a gate and a source that are located on a first surface of the first die and a drain that is located on a second surface of the first die that is opposite the first surface. The gate and source are flip chip coupled to the lead frame. The stack die package can include a second die including a gate and a drain that are located on a first surface of the second die and a source that is located on a second surface of the second die that is opposite the first surface. The source of the second die is facing the drain of the first die.