Stack Die Package Flip Chip Coupling Lead Frame
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Solution Overview
Problem
Conventional die packages, such as PPAIR and stack die packages, face limitations in die size due to wire bonding and soldering processes, which affect assembly yield and reliability, and increase costs due to silver plating requirements.
Innovation Solution
The proposed stack die package employs flip chip coupling of dies to a lead frame, eliminating wire bonding and reducing the need for silver plating, allowing for larger die sizes and improved assembly efficiency by using clips and solder pastes for electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is used in conventional die packages, then electrical connections can be established, but die size is limited and assembly yield and reliability are affected
Solution Approach 1:
The patent extracts and eliminates the wire bonding process from the packaging method. Instead of using wire bonds to connect dies to the lead frame, the invention directly bonds the die pads to the lead frame pads through a substrate, removing the intermediate wire bonding step that limited die size and reduced reliability.
Solution Approach 2:
The patent transitions from planar wire bonding connections to a three-dimensional stacked architecture where multiple dies are vertically arranged and bonded to the lead frame through a substrate. This dimensional change allows larger die sizes while maintaining reliable electrical connections.
2Ease of manufacture
If soldering process is used for clips in stack die packages, then electrical connections are established, but wire bond pad surfaces and lead post are contaminated
Solution Approach 1:
The patent extracts and eliminates the soldering process entirely from the assembly method. Instead of soldering clips to establish electrical connections, the invention uses direct bonding of die pads to lead frame pads through the substrate, removing the harmful soldering step that causes contamination.
Solution Approach 2:
The patent replaces the thermal soldering process with a mechanical/direct bonding process. The die pads are directly bonded to the lead frame pads through the substrate without requiring solder, eliminating the contamination associated with soldering while maintaining electrical connectivity.
3Ease of manufacture
If silver plating is applied on 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 requirement for silver plating on the lead frame. By removing wire bonding from the process and using direct bonding of die pads to lead frame pads, the invention eliminates the need for silver plating, thereby reducing lead frame cost.
Solution Approach 2:
The patent uses a standard lead frame without expensive silver plating by eliminating wire bonding. The direct bonding approach allows the use of simpler, less expensive lead frame materials and processing, reducing overall manufacturing cost.
Data Source
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.