Metallic Bolstering Pattern for Redistribution Layer Cracking Prevention
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Solution Overview
Problem
Current semiconductor package fabrication methods face challenges in ensuring the reliability and structural integrity of redistribution layers, particularly under thermal cycles and mechanical stress, which can lead to interface delamination and cracking.
Innovation Solution
The introduction of bolstering patterns between semiconductor dies and redistribution layers, which are electrically isolated and function as a structural reinforcing element, helps prevent cracking and enhances the reliability of the package by distributing stress and acting as a ground plane to reduce signal cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If redistribution layers are formed with fine-line patterns to achieve high integration, then packaging density and electrical performance are improved, but structural integrity and resistance to thermal-mechanical stress deteriorate
Solution Approach 1:
The redistribution layer structure is segmented into multiple functional components: the primary redistribution layer for electrical routing, and separate bolstering patterns positioned at strategic locations to provide mechanical support. This segmentation allows the thin fine-line redistribution patterns to maintain electrical functionality while the discrete bolstering elements provide localized structural reinforcement against thermal-mechanical stress.
Solution Approach 2:
The package structure employs composite material architecture by combining the conductive redistribution layer materials (typically copper or aluminum) with structurally robust bolstering patterns made from stress-resistant materials. This composite approach creates a multi-functional structure where different material properties are optimized for their specific roles: electrical conductivity for signal routing and mechanical strength for stress resistance.
2Length of stationary object
If thin redistribution layers are used to reduce package height, then package profile is improved, but resistance to interface delamination and cracking deteriorates
Solution Approach 1:
Bolstering patterns are formed in advance during the redistribution layer fabrication process, positioned at locations where thermal-mechanical stress is expected to concentrate. These pre-positioned structural reinforcements act as preventive measures against future delamination and cracking, allowing the thin redistribution layer to maintain its low-profile advantage while being protected from stress-induced failures.
Solution Approach 2:
The bolstering patterns serve as intermediary structural elements between the thin redistribution layer and the underlying substrate or adjacent components. These intermediate bolstering structures absorb and distribute mechanical stress, preventing direct stress transmission to the delicate redistribution layer interfaces and thereby reducing delamination and cracking risks.
3Reliability
If metallic bolstering patterns are added to reinforce redistribution layers, then structural integrity and reliability are improved, but device complexity and manufacturing steps increase
Solution Approach 1:
The formation of bolstering patterns is merged with the existing redistribution layer fabrication process sequence. The bolstering patterns are created using the same photolithography and deposition equipment and processes that are already employed for the redistribution layers, combining multiple functions into a single integrated manufacturing flow. This merging approach adds minimal process complexity while achieving the desired structural reinforcement.
Solution Approach 2:
The metallic patterns serve multiple functions simultaneously: they provide mechanical bolstering support to prevent delamination and cracking, act as ground planes to reduce signal cross-talk, and can serve as part of the electrical interconnect structure. This multi-functionality reduces the need for separate dedicated reinforcement structures, thereby limiting the increase in device complexity.
4Strength
If bolstering patterns are extended beyond die borders to maximize stress distribution, then cracking prevention is improved, but manufacturing alignment precision requirements increase
Solution Approach 1:
The bolstering patterns exhibit local quality variations in their geometry and material properties. The patterns are designed with different dimensions, thicknesses, and material compositions at different locations based on the specific stress distribution requirements. Areas requiring maximum stress resistance have more robust bolstering features, while areas with lower stress demands have reduced bolstering, optimizing both cracking resistance and manufacturing feasibility.
Data Source
AI summary
A package has a first semiconductor die, a second semiconductor die, a redistribution structure and a metallic bolstering pattern. The second semiconductor die is disposed beside the first semiconductor die and spaced apart from the first semiconductor die with a distance. The redistribution structure is disposed over the first semiconductor die and the second semiconductor die and is electrically connected with the first and second semiconductor dies. The metallic bolstering pattern is disposed between the redistribution structure and the first and second semiconductor dies. The metallic bolstering pattern is disposed on the redistribution structure and located over the first and second semiconductor dies, and the metallic bolstering pattern extends across the distance between the first and second semiconductor dies and extends beyond borders of the first and second semiconductor dies.