Flipchip Bump Patterns for Power Distribution
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Solution Overview
Problem
Traditional flipchip configurations require a dedicated silicon layer for power and ground bumps, limiting signal routing and increasing metal density, voltage drops, and package inductance due to alternating bump arrangements and metal extension tabs.
Innovation Solution
Power and ground bumps are arranged in a striped configuration, interconnected by mesh core busses without metal tabs, allowing signal routing and reducing metal requirements on upper layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alternating power and ground bump arrangement is used, then power distribution is achieved, but signal routing resources are reduced and metal density increases
Solution Approach 1:
The bump array is segmented into distinct power bump regions and ground bump regions rather than alternating them. Power bumps are grouped together in rows or blocks, and ground bumps are grouped together in separate rows or blocks, eliminating the need for interleaved metal extension tabs and reducing metal density requirements.
2Reliability
If alternating power and ground bump arrangement is used, then power distribution is achieved, but voltage drops increase due to metal extension tabs
Solution Approach 1:
The problematic metal extension tabs are extracted/removed from the design. By grouping power bumps together and ground bumps together, the need for metal extension tabs to bridge alternating power and ground bumps is eliminated, thereby removing the source of voltage drops associated with these tabs.
3Reliability
If alternating power and ground bump arrangement is used, then power distribution is achieved, but package inductance increases
Solution Approach 1:
The bump configuration is segmented into contiguous power regions and contiguous ground regions. This segmentation allows for more efficient via hole placement and package plane design, reducing the inductive paths that arise from alternating bump arrangements where via holes must be created in package power planes to escape alternating bumps.
4Reliability
If top-most metal layer is fully utilized for power distribution, then power mesh performance is improved, but signal routing resources are reduced
Solution Approach 1:
The top-most metal layer is segmented into dedicated power distribution regions and dedicated signal routing regions. By grouping power bumps together rather than alternating them with ground bumps, contiguous areas are created that can be used for either power distribution or signal routing, providing design flexibility and resource optimization.
Data Source
AI summary
Disclosed is a flipchip scheme where power and ground bumps are arranged in a striped configuration. Specifically, there are a plurality of lines of power bumps, and a plurality of lines of ground bumps. Each line of power bumps is interconnected by a mesh core power bus, and each line of ground bumps is interconnected by a mesh core ground bus. The busses are shorted across the bumps without having to use metal tab extensions. This arrangement provides that: signal routing can be provided between the lines of bumps; and/or the mesh core power busses can be provided as being wider in order to provide improved power mesh performance and/or in order to reduce or eliminate the metal required on the second top-most metal layer.