Power Semiconductor Package with Downset Die Attach Pad
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional power semiconductor packages with an isolated die attach pad face challenges in maintaining low thermal resistance and mechanical tolerance due to the unsupported die attach pad during molding, which increases the thickness of the molding compound and costs, and requires longer creepage distances, affecting thermal efficiency and package size.
Innovation Solution
The semiconductor package design incorporates a downset die attach pad supported by tie bars during molding, with notches or protrusions to reduce the creepage distance and minimize the package volume, allowing for a thinner molding compound and increased die attach pad area while meeting creepage requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the die attach pad is electrically isolated from the heatsink with a thin layer of molding compound, then the thermal resistance between die attach pad and mounting surface is reduced, but the mechanical tolerance increases due to the unsupported die attach pad during molding
Solution Approach 1:
The patent applies preliminary action by providing support structures (ties or anchors) that are pre-configured to hold the die attach pad in a predetermined position before molding begins. This prevents the die attach pad from moving or deforming during the molding process, ensuring mechanical tolerance is maintained while still allowing the molding compound to be placed between the die attach pad and mounting surface for electrical isolation.
2Ease of manufacture
If the die attach pad is mechanically held at only one end during molding, then the manufacturing process is simpler, but the mechanical tolerances increase significantly
Solution Approach 1:
The patent applies segmentation by dividing the support function into multiple segments or support points along the die attach pad. Instead of a single support point, multiple ties or anchors are distributed along the die attach pad, providing comprehensive support while maintaining manufacturing simplicity. This segmented approach prevents deformation and maintains tight tolerances without requiring complex single-point positioning mechanisms.
3Manufacturing precision
If the molding compound thickness is increased to support the die attach pad, then mechanical tolerance is improved, but the thermal resistance increases
Solution Approach 1:
The patent introduces an intermediary support structure (ties or anchors) that acts as a mediator between the die attach pad and the molding compound. This intermediary provides the necessary mechanical support and position control without requiring increased molding compound thickness. The support structures transfer mechanical loads and maintain positioning while allowing the molding compound to remain thin, thus maintaining low thermal resistance.
4Reliability
If the creepage distance is increased to meet minimum requirements, then electrical isolation is improved, but the package volume increases
Solution Approach 1:
The patent applies parameter changes by modifying the configuration and positioning of the die attach pad, leads, and support structures to optimize the creepage distance. By changing the geometric parameters and spatial arrangement of these components, the design achieves adequate electrical isolation (creepage distance) while minimizing the overall package volume. This may involve adjusting the orientation, location, or dimensions of various elements to create a more compact layout that still meets isolation requirements.
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 design enhances thermal efficiency by reducing the package volume and molding compound usage, minimizing costs, and maintaining adequate creepage distances, thus optimizing the balance between thermal performance and cost-effectiveness.
Implementation Method 1
A molding compound encapsulates the semiconductor die and a portion of the leads which may extend beyond the outside of the package for electrical connection to external circuitry
Implementation Method 2
the package is also designed with a mounting surface for physical attachment to a heat sink that is designed as the primary path for transfer of the heat generated by the power device away from the semiconductor die
Data Source
AI summary
A package for a semiconductor die includes a die attach pad that provides an attachment surface area for the semiconductor die, and tie bars connected to the die attach pad. The die attach pad is disposed in a first general plane and the tie bars are disposed in a second general plane offset with respect to the first general plane. A molding compound encapsulates the semiconductor die in a form having first, second, third and fourth lateral sides, a top and a bottom. The tie bars are exposed substantially coincident with at least one of the lateral sides. The form includes a discontinuity that extends along the at least one of the lateral sides, the discontinuity increasing a creepage distance measured from the tie bars to the bottom of the package.