Semiconductor Package Stiffening Ring for Heat Spreader Warpage
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Solution Overview
Problem
Semiconductor packages face challenges with warpage and stress issues due to thermal expansion, which affect the reliability and performance of the package during temperature cycling, and there is a need for improved rigidity and surface area for mounting passive components.
Innovation Solution
A semiconductor package design incorporating a heat spreader with a peripheral side wall portion and a stiffening ring with a central opening, positioned close to the semiconductor die, along with tie bars between inner and outer ring portions, to provide structural support and efficient installation of passive components, while using a thermally conductive material for heat management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat spreader is attached to the substrate board, then heat management is improved, but warpage and stress issues worsen due to thermal expansion
Solution Approach 1:
The stiffener is divided into an inner ring portion and an outer ring portion connected by tie bars, creating a segmented structure that can independently manage different stress zones. The inner ring supports the heat spreader while the outer ring provides overall package stability, and tie bars transfer thermal expansion stresses between them, resolving the contradiction between heat management and warpage control.
Solution Approach 2:
The stiffener structure provides different levels of support at different locations: the inner ring portion directly supports the heat spreader where thermal expansion is most severe, while the outer ring portion provides general structural stability. This localized quality distribution allows the heat spreader to function effectively while preventing overall package warpage.
2Ease of manufacture
If the package structure is simplified, then manufacturing ease is improved, but surface area for mounting passive components is reduced
Solution Approach 1:
The stiffener is segmented into inner and outer ring portions with tie bars, creating distinct functional zones. The inner ring maintains a central opening that preserves substrate surface area for component mounting, while the outer ring provides structural support. This segmentation allows both manufacturing simplicity and adequate mounting surface area.
Solution Approach 2:
The stiffener extends in multiple dimensions with its inner ring, outer ring, and connecting tie bars, creating a three-dimensional framework that provides structural support without occupying excessive two-dimensional surface area on the substrate. This dimensional approach maximizes the available mounting surface while maintaining package rigidity.
3Stability of the object's composition
If a stiffener is added to reduce warpage, then package rigidity is improved, but device complexity increases
Solution Approach 1:
The stiffener structure serves multiple functions simultaneously: the inner ring supports the heat spreader, the outer ring provides overall package stability, and the tie bars transfer thermal expansion stresses. This multi-functionality achieves high package rigidity without requiring multiple separate components, thereby limiting the increase in device complexity.
Solution Approach 2:
The inner ring, outer ring, and tie bars are merged into a single integrated stiffener component that can be manufactured as one piece or pre-assembled unit. This merging reduces the number of separate parts and assembly steps compared to using multiple independent stiffening elements, thus improving package rigidity while controlling device 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
The design significantly reduces warpage and stress on the semiconductor die, improves package rigidity, and increases the surface area for mounting passive components, resulting in enhanced performance during temperature cycling.
Implementation Method 1
A thermally conductive material (20) (also known in the art as a thermal interface material), which may also comprise an adhesive, is positioned between a top surface of the die 12 and a bottom surface of the heat spreader 18
Implementation Method 2
a heat spreader (18), attached to the top surface of the substrate board, the heat spreader including a plate portion integrally formed with a peripheral side wall portion
Data Source
Figure 1~3
Figure 4~5
Figure 6~10
AI summary
A semi-conductor package is provided including a substrate board and a semiconductor die attached to a surface of the substrate board. A heat spreader, attached to the top surface of the substrate board is provided. The heat spreader includes a plate portion integrally formed with a peripheral side wall portion. The semi-conductor package having a stiffener comprising a stiffening ring, with an I-shaped cross section, having a central opening sized and shaped to fit around said semiconductor die within the package, the stiffening ring having at least a vertical and a horizontal leg sized and shaped to provide a space between an inner edge of the wall portion of said heat spreader and the vertical leg of the stiffening ring wherein the space permits the installation of passive electrical components, at least partially below the horizontal portion of the stiffening ring and on the surface of the substrate board.