Stack Die Package Flip Chip Clip Connections
Find Innovative SolutionsGenerate Solutions
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 lead frame costs.
Innovation Solution
The method involves coupling the gate and source of one die to a lead frame, with the drain on an opposite surface, and coupling the source of a second die to the drain of the first, eliminating wire bonding by using flip chip technology and clips for electrical connections, allowing for larger die sizes and reduced assembly costs.
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 between dies and lead frame, but the die size is limited and assembly complexity increases
Solution Approach 1:
The patent transitions from planar wire bonding to three-dimensional flip-chip stacking, where dies are vertically stacked and connected through substrate through-holes. This dimensional change allows larger die areas while reducing assembly complexity by eliminating wire bonding operations.
Solution Approach 2:
The invention extracts and eliminates the wire bonding process entirely by using direct flip-chip bonding with clips that connect through substrate holes. This removes the harmful wire bonding step while enabling larger die sizes and simpler assembly.
2Reliability
If soldering process is used for clip attachment, then clips can be securely attached to dies, but wire bond pad surfaces and lead posts become contaminated
Solution Approach 1:
The patent introduces an intermediary refractory metal coating (such as tungsten, molybdenum, or tantalum) between the solder and the wire bond pad surfaces. This intermediary layer prevents solder contamination of critical bonding surfaces while still allowing secure clip attachment through the substrate through-holes.
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 invention extracts and eliminates the need for silver plating on the lead frame by completely removing the wire bonding process. The flip-chip clipping method uses standard lead frame materials without requiring expensive silver plating, thereby reducing material costs while maintaining manufacturing capability.
Data Source
AI summary
In one embodiment, a method can include coupling a gate and a source of a first die to a lead frame. The first die can include the gate and the 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. In addition, the method can include coupling a source of a second die to the drain of the first die. The second die can include a gate and the source that are located on a first surface of the second die and a drain that is located on a second surface of the second die that is opposite the first surface.