Semiconductor Package Underfill Stress-Release Structure for Crack Mitigation
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Solution Overview
Problem
Integrated circuit packages experience cracking due to material differences between components, which worsens with increasing package size.
Innovation Solution
Incorporation of a stress-releasing structure within the underfill material between semiconductor packages and substrates, utilizing stress-release-blocks with specific material properties to mitigate cracking.
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 becomes more severe
Solution Approach 1:
The patent introduces a stress-releasing structure that segments the continuous underfill material into distinct regions. This segmentation allows different portions of the underfill to move independently, accommodating thermal expansion differences and reducing stress concentration that would otherwise lead to cracking in large packages.
Solution Approach 2:
The stress-releasing structure creates localized regions with different mechanical properties within the underfill material. These local modifications provide stress relief precisely where needed (at the stress-releasing structure) while maintaining the integrity of the surrounding underfill, enabling the package to handle larger sizes without proportional increases in cracking risk.
2Adaptability or versatility
If package size is increased to improve functionality and integration level, then the functionality and integration level are improved, but structural integrity deteriorates
Solution Approach 1:
By segmenting the underfill structure through the stress-releasing feature, the patent prevents crack propagation across the entire package. The segmentation creates discrete zones that can deform independently, maintaining overall structural integrity even as package size increases and thermal stresses accumulate.
Solution Approach 2:
The stress-releasing structure acts as a pre-positioned cushioning element that anticipates and mitigates thermal stress before it can cause damage. This proactive stress management preserves structural integrity in large packages by providing a designated stress relief pathway before cracking can occur.
3Reliability
If stress-releasing structure is added to reduce cracking, then cracking resistance is improved, but device complexity increases
Solution Approach 1:
The stress-releasing structure serves as an intermediary element between the underfill material and the potential crack propagation path. This intermediate structure absorbs and redistributes stress, preventing direct crack formation without requiring fundamental changes to the entire package design, thus limiting the increase in complexity.
Solution Approach 2:
The stress-releasing structure functions as a flexible element within the underfill that can deform to accommodate thermal expansion differences. This flexible approach provides cracking resistance through controlled deformation rather than rigid resistance, adding minimal complexity while effectively managing stress 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
Reduces the risk of cracks by distributing stress more effectively, enhancing the structural integrity of large semiconductor packages.
Implementation Method 1
a first dielectric block protruding from the first polymer layer... an underfill material between the at least one semiconductor chip and the device substrate, wherein the underfill material encapsulates the first dielectric block
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.