Curved-Corner Die Stack Structure for Thermal Stress Relief
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving smaller, faster, and more energy-efficient packaging techniques due to issues with stress-induced cracks and delamination in die stack structures caused by coefficient of thermal expansion (CTE) mismatch, particularly at sharp corners of semiconductor dies.
Innovation Solution
A die stack structure is designed with non-sharp corners and a redistribution layer, where the first die has a stepped profile with curved side surfaces, and an encapsulant that laterally encapsulates the second and third dies, reducing stress and preventing cracks and delamination by distributing thermal expansion evenly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sharp corners are used in die stack structures, then manufacturing precision is improved, but stress concentration occurs leading to cracks and delamination
Solution Approach 1:
The patent applies curvature by replacing sharp corners with rounded corners in the die stack structure. Specifically, the encapsulant is configured to have a rounded corner profile at the corners of the die stack, which distributes stress evenly and prevents stress concentration that would occur at sharp corners. This curvature modification eliminates the harmful stress concentration effect while maintaining structural integrity and reliability.
2Area of moving object
If die stack structures are used for miniaturization, then integration density is improved, but thermal expansion mismatch causes stress-induced cracks
Solution Approach 1:
The patent modifies the geometric parameters of the die stack structure by implementing rounded corners instead of sharp corners. This parameter change affects the stress distribution characteristics, transforming the stress field from concentrated at sharp corners to distributed along the rounded profile. The rounded corner design changes the local geometry to accommodate thermal expansion differences between stacked dies, preventing crack initiation while maintaining the miniaturized high-density integration.
3Strength
If encapsulant is added to laterally encapsulate dies, then structural support is improved, but stress concentration at corners increases
Solution Approach 1:
The patent directly addresses the stress concentration problem by configuring the encapsulant with rounded corners. The rounded corner profile of the encapsulant eliminates sharp geometric transitions that would concentrate stress. This curvature design allows the encapsulant to provide structural support and protection while distributing mechanical and thermal stresses evenly across the corner regions, preventing the stress concentration that would otherwise occur at sharp corners.
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 configuration effectively suppresses stress-related issues like cracks and delamination, enhancing the reliability and performance of the die stack structure by eliminating sharp corners and managing thermal expansion mismatch.
Implementation Method 1
coefficient of thermal expansion (CTE) mismatch
Implementation Method 2
distributing thermal expansion evenly
Data Source
AI summary
A die stack structure including a first die, an encapsulant, a redistribution layer and a second die is provided. The encapsulant laterally encapsulates the first die. The redistribution layer is disposed below the encapsulant, and electrically connected with the first die. The second die is disposed between the redistribution layer and the first die, wherein the first and second dies are electrically connected with each other, the second die comprises a body portion having a first side surface, a second side surface and a curved side surface therebetween, and the curved side surface connects the first side surface and the second side surface.