Semiconductor Package Underfill Segmentation for Thermal Crack Relief
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Solution Overview
Problem
Integrated circuit packages face cracking issues due to material differences between components, which worsen with increasing package size, leading to stress-related problems.
Innovation Solution
A stress-releasing structure is integrated within the underfill material between the semiconductor package and the substrate, using a core substrate with redistribution structures and conductive vias, and stress-release-blocks formed through photolithographic processes to mitigate thermal expansion differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If package size is increased to improve functionality and integration level, then the functionality and integration level are improved, but cracking severity increases due to material differences between package components
Solution Approach 1:
The patent introduces a stress-releasing structure that segments the continuous underfill material into distinct regions separated by voids or channels. This segmentation allows different parts of the underfill to move independently, accommodating thermal expansion differences between package components and preventing crack propagation across the entire package, thus resolving the contradiction between large package size and cracking resistance
Solution Approach 2:
The stress-releasing structure creates localized regions with different mechanical properties within the underfill material. The voids or channels are strategically positioned at critical stress points (such as corners and interfaces between different materials) to provide local stress relief, allowing the package to maintain overall structural integrity while managing localized thermal stress concentrations
2Adaptability or versatility
If package size is increased to improve functionality, then the functionality is improved, but stress-related problems become more severe
Solution Approach 1:
The stress-releasing structure acts as an intermediary element within the underfill material that mediates the thermal stress between different package components. The voids or channels provide a buffer zone that absorbs and distributes thermal stress, preventing direct stress transmission between materials with different coefficients of thermal expansion, thus reducing overall stress-related problems in large packages
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 solution effectively reduces the risk of underfill cracking by 11% at the package corners, providing a cost-effective method to manage thermal stress in large semiconductor packages.
Implementation Method 1
mitigate thermal expansion differences
Data Source
AI summary
Package structures and methods of forming package structures are discussed. A package structure, in accordance with some embodiments, includes a large package component, such as a CoWoS, adhered to a large package substrate, such as a printed circuit board, an underfill material disposed between the large package component and the large package substrate, and a stress-release structure with high elongation values formed from photolithography encapsulated by the underfill material. The stress-release structure helping to reduce stress in the underfill material to reduce the risk of underfill cracking caused by the difference in coefficients of thermal expansion between the large package component and the large package substrate.