Mixed BGA Pad Layout for RF Reliability and Footprint Reduction
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Solution Overview
Problem
Conventional flip-chip packaging designs face challenges in meeting the performance demands of RF front-end devices, particularly in board level reliability and footprint reduction for 5G applications, due to limitations in uniform solder mask defined BGA pad approaches.
Innovation Solution
The implementation of a mixed pad size and pitch configuration, combining solder mask defined (SMD) and non-solder mask defined (NSMD) pads, allows for greater design control and increased reliability by varying pad size and pitch, enabling larger pads for power and RF signals while maintaining higher density for other signaling needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform SMD BGA pad design is used, then manufacturing simplicity is maintained, but footprint reduction and board level reliability for RF applications deteriorate
Solution Approach 1:
The patent applies local quality by implementing different pad designs (SMD and NSMD) in different regions of the package substrate. Specifically, digital signal pads use one design while RF front-end pads use another design optimized for RF performance, allowing each region to have the quality characteristics needed for its specific function.
Solution Approach 2:
The patent segments the pad array into distinct groups with different characteristics. The package substrate is divided into regions with different pad sizes, pitches, and solder mask configurations, allowing optimization of specific areas for RF applications while maintaining standard designs for digital I/O.
2Device complexity
If uniform pad size is used across the whole chip, then design simplicity is maintained, but footprint reduction for RF front-end devices deteriorates
Solution Approach 1:
The patent implements local quality by varying pad sizes based on location and function. RF front-end pads are positioned at the periphery with larger sizes and different pitch to accommodate RF performance requirements, while digital pads in the center use smaller uniform sizes, thereby reducing overall footprint while meeting RF demands.
3Reliability
If larger pads are used for RF signals, then signal integrity improves, but pad density for other signaling needs deteriorates
Solution Approach 1:
The patent segments the pad array into RF-specific regions and digital I/O regions. RF pads are concentrated at the periphery with larger sizes optimized for signal integrity, while the central area maintains high-density smaller pads for digital signaling, thus satisfying both requirements simultaneously.
Solution Approach 2:
The patent utilizes spatial dimensionality by positioning RF pads at the periphery and digital pads in the center, creating a radial distribution pattern. This dimensional arrangement allows large RF pads without compromising the pad density in the central region, as the two functions occupy different spatial zones.
Data Source
AI summary
Disclosed is a package and method of forming the package with a mixed pad size. The package includes a first set of pads having a first size and a first pitch, where the first set of pads are solder mask defined (SMD) pads. The package also includes a second set of pads having a second size and a second pitch, where the second set of pads are non-solder mask defined (NSMD) pads.