Offset Leadframe Cascode Package Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor devices face challenges in achieving effective isolation between high-voltage and low-voltage transistors in power electronic circuits, often requiring additional components like bonded copper ceramic isolators, which can be costly and complex to implement.
Innovation Solution
A composite semiconductor device is constructed in a single package by mounting high-voltage and low-voltage dies on separate planar substrates with a dielectric encapsulant gap, using a metallic leadframe with removable tie-bars to create vertical and lateral spacing, eliminating the need for separate isolation components and allowing for standard package formats like TO-220 or TO-247.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate isolation components like bonded copper ceramic isolators are used to achieve effective isolation between high-voltage and low-voltage transistors, then isolation reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the isolation function with the substrate structure itself by creating a through-substrate via that passes completely through the substrate thickness, integrating the isolation mechanism into the substrate rather than using separate isolation components. This merging of functions reduces device complexity while maintaining isolation reliability.
Solution Approach 2:
The patent extracts the isolation function from separate components and implements it directly within the substrate structure through the through-substrate via design, eliminating the need for additional bonded copper ceramic isolators and reducing overall device complexity.
2Reliability
If separate isolation components are used to achieve voltage isolation, then isolation effectiveness is improved, but manufacturing cost increases
Solution Approach 1:
The isolation function is merged into the substrate structure through the through-substrate via, eliminating the need for separate isolation components and reducing manufacturing cost while maintaining voltage isolation effectiveness.
Solution Approach 2:
The substrate serves multiple functions: it provides mechanical support, electrical connections through vias, and voltage isolation through the through-substrate via design. This multi-functionality reduces the need for additional components and lowers manufacturing cost.
3Productivity
If a single leadframe is used for multiple devices with removable tie-bars, then manufacturing efficiency is improved, but assembly complexity increases
Solution Approach 1:
The leadframe is segmented into multiple regions with removable tie-bars that can be selectively removed to separate individual devices or keep them connected. This segmentation allows flexible assembly configurations while maintaining manufacturing efficiency through the shared leadframe structure.
Solution Approach 2:
The tie-bars are designed to be removable, providing dynamic flexibility in assembly. The leadframe structure can be configured as either connected or separated devices depending on the application requirements, allowing adaptive assembly without increasing overall complexity.
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 solution provides enhanced isolation between high-voltage and low-voltage transistors without additional isolation components, improving manufacturing efficiency and reducing costs by using a single leadframe for multiple devices, while maintaining thermal performance and achieving high dielectric strength for voltage isolation.
Implementation Method 1
a dielectric encapsulant... providing a dielectric gap between the substrates
Implementation Method 2
The leadframe may be metallic, such that the regions and the tie-bars together form a contiguous metallic structure
Data Source
AI summary
A composite semiconductor device, such as a high-voltage cascode, is constructed in a single package by mounting a first die on a first planar substrate and second die mounted on a second planar substrate, where the substrates are separated by a gap filled with a dielectric encapsulant. The substrates may be separated both vertically and as well as laterally, to lie in different parallel planes. The substrates are in a leadframe that also includes interconnections, heat sinks, package pins, and removable tie-bars, forming a contiguous metallic structure. Multi-device frames containing multiple leadframes joined by additional tie-bars may be used to process multiple composite semiconductor devices together in, e.g., step-and-repeat wire and die bonding processes and batch encapsulation molding batch processes.