Substrate Structure with Obtuse Portion for Stress Dispersion
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Solution Overview
Problem
In semiconductor packaging, the mismatch in thermal expansion coefficients between chips and package substrates leads to thermal stress, warpage, and poor bonding, resulting in reliability issues and product failures due to cracks at corners during temperature cycles or stress variations.
Innovation Solution
A substrate structure with an obtuse portion featuring multiple turning surfaces is introduced, which disperses stress by modifying the substrate's geometry, reducing the likelihood of cracks and improving bonding reliability through the fabrication method of forming concave portions and cutting the substrate module along these surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional rectangular substrate corners are used, then manufacturing is simple, but stress concentration occurs at corners causing cracks during temperature cycles
Solution Approach 1:
The patent applies curvature by replacing sharp rectangular corners with rounded corners having a specified radius (e.g., R1, R2, R3, R4). This curvature eliminates stress concentration points that would otherwise occur at sharp corners during thermal expansion and contraction, thereby preventing cracks while maintaining manufacturability through standard PCB routing and drilling processes.
2Strength
If substrate thickness is increased to improve strength, then crack resistance improves, but warpage due to thermal expansion mismatch increases
Solution Approach 1:
The patent introduces asymmetry by creating non-uniform thickness distribution across the substrate. Specific regions (such as corner areas or areas with openings) have different thicknesses than other regions. This asymmetric thickness design allows stress distribution optimization - thicker areas provide strength and crack resistance, while thinner areas reduce overall thermal mass and warpage potential.
Solution Approach 2:
The patent applies local quality by varying substrate thickness and material properties at specific locations rather than uniformly across the entire substrate. For example, corner regions may have different thickness or material composition compared to central regions, allowing each area to be optimized for its specific functional requirements - strength where needed, flexibility where beneficial.
3Stability of the object's composition
If substrate flexibility is increased to reduce warpage, then thermal stress decreases, but mechanical strength and crack resistance deteriorate
Solution Approach 1:
The patent employs composite materials by combining multiple materials with different thermal expansion coefficients and mechanical properties within the substrate structure. This allows the substrate to have regions with high flexibility (lower modulus materials) to reduce warpage, while other regions maintain high strength (higher modulus materials) for crack resistance. The composite structure achieves a balance between flexibility and strength that neither material could provide alone.
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 substrate structure effectively disperses stress, reducing the occurrence of cracks and enhancing product yield by eliminating stress concentration at corners and edges, thereby improving the reliability of semiconductor packages.
Implementation Method 1
The substrate structure effectively disperses stress, reducing the occurrence of cracks and enhancing product yield by eliminating stress concentration at corners and edges
Data Source
AI summary
A substrate structure has an obtuse portion formed between a side surface and a bottom surface of a substrate body. The obtuse portion includes a plurality of turning surfaces to disperse the stress of the substrate body generated in the packaging process. Therefore, the substrate body is prevented from being cracked. A method for fabricating the substrate structure and an electronic package including the substrate structure are also provided.