Flexible UBM Layout for Reduced Die Bump Pitch
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Solution Overview
Problem
Conventional integrated circuit (IC) packages face challenges in reducing die bump pitch to minimize die area and increase interconnect density, as it often results in reduced yield and higher assembly costs, especially in RF technology where bump keep-out-zones and fabrication process limitations are significant.
Innovation Solution
The implementation of flexible under-bump metallization (UBM) sizes and patterning, including mixed UBM sizes and oblong-shaped UBMs, to facilitate reduced pitch without compromising reliability, allowing for more efficient signal routing and increased interconnect density by strategically placing smaller UBMs in the core and periphery areas of the die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If die bump pitch is reduced to conserve die area and increase interconnect density, then die area is reduced and interconnect density is increased, but yield is reduced and assembly costs increase
Solution Approach 1:
The patent applies different UBM sizes (first UBM size and second UBM size) in different regions of the die to optimize local interconnect requirements. Larger UBMs are used where higher reliability is needed, while smaller UBMs are used where space is constrained, allowing reduced pitch without uniformly compromising yield across the entire die.
Solution Approach 2:
The die is segmented into different regions with different UBM pitch configurations. First UBMs are arranged with a first pitch while second UBMs are arranged with a second pitch, allowing different areas to be optimized for different functions - some areas for high-density interconnects, others for high-reliability connections.
2Quantity of substance
If die bump pitch is reduced to increase interconnect density, then interconnect density is increased, but assembly costs increase
Solution Approach 1:
Different UBM sizes and pitches are applied locally to match different interconnect density requirements. This allows high interconnect density in regions where it is needed while maintaining manufacturable pitch in regions where assembly complexity would otherwise increase, thereby controlling overall assembly costs.
3Area of moving object
If mixed UBM sizes are used to route different signal types, then die area is minimized and signal routing is optimized, but UBM patterning complexity increases
Solution Approach 1:
The UBM array is segmented into different types (first UBMs and second UBMs) with different sizes and pitches, allowing optimization for different signal routing requirements. This segmentation enables compact die layout while the modular nature of the segmented UBM structure helps manage patterning complexity through systematic design.
Solution Approach 2:
The patent introduces variation in UBM size (a dimensional parameter) in addition to spatial arrangement, creating a two-dimensional optimization space (position and size) that enables area minimization while the regular patterning of different UBM types provides a systematic approach that manages fabrication complexity.
Data Source
AI summary
Flexible under-bump metallization sizes and patterning, and related integrated circuit packages and fabrication methods are disclosed. First under-bump metallizations (UBMs) of a first, larger size and pitch are provided in the die and coupled to corresponding metal interconnects in the package substrate. One or more second UBMs of a second, reduced size UBMs can also be located in the core area of the die. This provides greater flexibility in the design and layout of the die, because different circuits within the die (e.g., I/O related circuits) may only require coupling to smaller size UBMs for performance requirements and thus can be more flexibility located in the die. Also, to further reduce pitch of the second, smaller size UBMs, one or more of the second, smaller size UBMs can be formed as oblong-shaped UBMs, which can still maintain a minimum separation based on metal interconnect pitch limitations in the package substrate.