BGA Land Pattern Optimization via Non-Fully Populated Edges
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Solution Overview
Problem
BGA packages face challenges in accommodating increasing IC die functions with larger I/O signals and powers while maintaining package size and reducing signal routing complexity, leading to increased costs and larger footprints.
Innovation Solution
The implementation of non-fully populated edge rows in contact pad arrays and land patterns creates additional signal routing channels, optimizing the number of spaces to enhance routing capacity without unnecessary increases, thereby reducing package size and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of I/O signals and power connections is increased to accommodate more IC die functions, then the functionality and performance of the IC package is improved, but the package size and PCB footprint increase
Solution Approach 1:
The patent utilizes multiple PCB layers to route signals, transitioning from a two-dimensional routing approach to a three-dimensional approach. By distributing I/O signals across multiple layers and using vertical vias to connect them, the design accommodates increased functionality without proportionally increasing the package footprint, as signals are routed through the depth of the PCB rather than only across its surface.
Solution Approach 2:
The patent segments the contact pad array into functional groups (I/O signals, power, ground) and distributes them across different PCB layers. This segmentation allows efficient utilization of available routing resources on each layer, enabling high-density interconnection without requiring a larger package area.
2Device complexity
If the package size is increased to accommodate more routing channels, then the signal routing capacity is improved, but the PCB footprint and manufacturing cost increase
Solution Approach 1:
The patent employs multi-layer PCB construction to provide additional routing dimensions. Signals that would require longer lateral paths on a single layer can instead be routed vertically through vias to adjacent layers, effectively increasing routing capacity without increasing the horizontal footprint of the package.
Solution Approach 2:
The patent designs the contact pad array and PCB interface to handle multiple signal types (I/O, power, ground) simultaneously through a unified multi-layer routing architecture. This multi-functional approach maximizes the utilization of available routing resources within the given footprint, accommodating complex signal routing without requiring additional package area.
3Device complexity
If the number of routing layers is increased to accommodate more signals, then the signal routing capacity is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent applies different routing strategies to different PCB layers based on local requirements. For example, inner layers may be dedicated to power and ground planes for optimal electrical performance, while outer layers handle I/O signals for easier external connectivity. This localized optimization allows efficient signal routing without uniformly increasing manufacturing complexity across all layers.
Solution Approach 2:
The patent performs preliminary routing planning during the design phase, systematically assigning signals to specific layers and via locations before manufacturing. This pre-planned approach to multi-layer routing minimizes manufacturing complexity by providing clear fabrication guidelines, reducing the need for complex post-processing or manual adjustments.
4Quantity of substance
If the contact pad array is fully populated to maximize I/O connections, then the connection density is improved, but the available routing channels at the perimeter are reduced
Solution Approach 1:
The patent compensates for reduced perimeter routing channels caused by full pad population by utilizing the vertical dimension through multiple PCB layers. Signals from fully populated contact pads are routed through vias to additional layers that provide dedicated routing channels, effectively increasing routing capacity without sacrificing contact pad density at the perimeter.
Data Source
AI summary
A method, system, for optimizing routing layers and board space requirements for a ball grid land pattern is described. A number of required pads is determined. A land pattern to yield the required pads is selected. A number of required perimeter routing channels is determined. A size of the land pattern to yield the required perimeter routing channels is optimized. At least one perimeter edge of the land pattern is under populated. In a further aspect, a number of layers is determined when a substrate has multiple layers.