Patterned Redistribution Pad for IC Package Stress Relief
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Solution Overview
Problem
Integrated circuit package systems face challenges in maintaining stability and small isolated feature deposition, particularly with early failures when reducing size while maintaining large bumps on redistribution layers for wafer level chip scale packages, which affects performance and cost efficiency.
Innovation Solution
The implementation of a patterned redistribution pad with openings and a second insulating layer that provides stress relief, improved adhesion, and even stress distribution for under bump layers, enhancing the reliability of conductive bumps and redistribution layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wafer level chip scale packages use large bumps on redistribution layers, then electrical connection and thermal conduction are improved, but manufacturing stability deteriorates due to early failures when reducing size
Solution Approach 1:
The redistribution layer is segmented into isolated pad regions separated by grooves or trenches. This segmentation isolates the bumps from each other and from the surrounding structure, preventing stress propagation and manufacturing defects from affecting the entire layer. Each pad region can be independently manufactured and tested, improving overall manufacturing stability while maintaining reliable electrical connections.
Solution Approach 2:
The patent applies different structural characteristics to different regions: the pad regions have high electrical conductivity for reliable connection, while the groove regions provide mechanical isolation and stress relief. This local differentiation allows large bumps to maintain their electrical and thermal functions while the surrounding structure is optimized for manufacturing stability and defect isolation.
2Area of stationary object
If the substrate area is reduced to increase integrated circuit density, then portability and real estate utilization are improved, but stress concentration increases leading to early failures
Solution Approach 1:
By dividing the substrate into isolated pad regions separated by grooves, the patent prevents stress from concentrating across the entire substrate area. Each isolated pad can accommodate thermal and mechanical expansion independently, reducing overall stress concentration even when the total substrate area is minimized for high density integration.
Solution Approach 2:
The grooves or trenches act as intermediary elements between adjacent pads and between the pads and the substrate edges. These intermediaries provide stress relief pathways and prevent direct stress transmission across the compact substrate, enabling high circuit density without compromising structural stability.
3Reliability
If conductive bumps are made larger to improve electrical and thermal conduction, then connection performance is improved, but manufacturing difficulty increases due to deposition challenges on small isolated features
Solution Approach 1:
The segmented pad structure with grooves creates well-defined, isolated deposition areas for the conductive bumps. This segmentation simplifies the manufacturing process by providing clear boundaries for bump formation, allowing standard deposition techniques to effectively create large, reliable bumps without the complexity of patterning across continuous large areas.
Solution Approach 2:
The patent creates locally optimized conditions for bump deposition by providing isolated pad regions with appropriate geometry and surface properties. Each pad region can be independently processed, allowing large bumps to be formed with controlled size and distribution, improving both manufacturing ease and bump performance.
Data Source
AI summary
An integrated circuit package system includes an integrated circuit, and forming a patterned redistribution pad over the integrated circuit.