Hybridization Bump Structure for Fine-Pitch Alignment Tolerance
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Solution Overview
Problem
Conventional flip-chip interconnects in infrared focal plane arrays face challenges with misalignment and weakened connections due to the need for high quality bump connections with large height-to-diameter ratios, leading to issues like shorted detectors and weakened bump connections in ultra-fine pitch arrays.
Innovation Solution
A hybridization system using bumps with different material hardness and diameters, where harder bumps with a c-shape penetrate softer bumps during alignment, accommodating misalignment and enhancing electrical contact area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If large bump height to diameter ratio is used to achieve high quality bump connection, then connection strength is improved, but alignment precision deteriorates due to increased sensitivity to misalignment
Solution Approach 1:
The bump connection system is segmented into two distinct bump types: a first bump with larger diameter and smaller height, and a second bump with smaller diameter and larger height. This segmentation allows each bump type to fulfill different functional requirements - the first bump provides alignment tolerance through its larger diameter, while the second bump provides connection strength through its larger height-to-diameter ratio.
Solution Approach 2:
Different local qualities are assigned to different bump positions. The first bumps (with larger diameter) are positioned where alignment tolerance is needed, while the second bumps (with larger height) are positioned where connection strength is critical. This local differentiation resolves the contradiction by optimizing each bump's geometry for its specific functional requirement.
2Reliability
If accurate alignment is required for high quality bump connection, then connection reliability is improved, but device complexity increases due to stricter alignment requirements
Solution Approach 1:
The connection system is divided into first bumps for alignment tolerance and second bumps for reliable electrical connection. This segmentation allows the system to achieve high connection reliability without requiring strict alignment across all bumps, thereby reducing device complexity and alignment requirements.
Solution Approach 2:
The first bumps with larger diameter act as intermediary elements that accommodate misalignment. They serve as a mediator between the substrate and the second bumps, absorbing alignment errors and enabling the second bumps to form reliable connections even when perfect alignment is not achieved.
3Productivity
If smaller bump diameter is used to increase pitch density, then productivity is improved, but alignment tolerance deteriorates
Solution Approach 1:
The bump array is segmented into two size categories: larger first bumps that provide alignment tolerance and smaller second bumps that enable high pitch density. This segmentation allows the system to achieve both high productivity through dense packing and adequate alignment tolerance through the presence of larger reference bumps.
Solution Approach 2:
Asymmetric bump sizing is employed where the first bumps have larger diameter than the second bumps. This asymmetry creates a hierarchical structure where larger bumps serve as alignment references and smaller bumps provide dense interconnections, resolving the contradiction between pitch density and alignment tolerance.
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 system improves alignment tolerance and electrical connectivity in ultra-fine pitch infrared focal plane arrays by reducing bump flattening and increasing contact area, thereby enhancing operability and performance.
Implementation Method 1
The first plurality of bumps have a different material hardness from the second plurality of bumps
Data Source
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AI summary
A system (100) includes a die (102) with a first plurality of hybridization bumps (104) extending therefrom, electrically connected to circuitry die (102). An external circuitry component (106) with a second plurality of hybridization bumps (108) extending therefrom, is electrically connected to circuitry in the external circuitry component (106). The first plurality of hybridization bumps (104) and the second plurality of hybridization bumps (108) are pressed together for electrical communication between the die (102) and the external circuitry component (106). The first plurality of hybridization bumps (104) have a different material hardness from the second plurality of hybridization bumps (108). The first plurality of hybridization bumps (104) have a different bump diameter (d, D) from that of the second plurality of hybridization bumps (108) .