Compound Via RF Transition Structure for High-Density Interconnects
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Solution Overview
Problem
Current semiconductor BGA device packages face limitations in high-frequency signal transmission due to deviations in signal path impedance, ball-to-ball capacitance, and parasitic effects, which restrict RF signal fidelity and bandwidth, especially at frequencies above 30 GHz.
Innovation Solution
The implementation of a multilayer circuit board design with a central conductor via array and strategically positioned ground protrusions to reduce capacitance and maintain optimal impedance, using compound vias and varying conductor diameters to minimize parasitic effects and enhance RF transmission characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional BGA device packages are used for high-frequency signal transmission, then device integration is achieved, but signal path impedance deviation and parasitic effects increase, degrading RF signal fidelity and bandwidth
Solution Approach 1:
The patent segments the via structure into multiple components: a first via portion through the substrate, a second via portion extending from the first, and a conductive ring connecting them. This segmentation allows each portion to be optimized for specific functions, reducing overall parasitic effects and impedance deviation in RF signal transmission
Solution Approach 2:
The patent implements nesting by placing the first via portion inside the second via portion, with the conductive ring connecting them. This nested configuration creates a controlled impedance path while minimizing parasitic capacitance and inductance, thereby improving RF signal fidelity at high frequencies
2Reliability
If small ball sizes are used to reduce ball-to-ball capacitance for high-frequency signals, then RF performance improves, but manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the via structural parameters by introducing a multi-segment via design with conductive rings, rather than relying solely on reducing ball size. This parameter change maintains low parasitic effects and good RF performance while allowing for larger, easier-to-manufacture via structures
3Reliability
If additional components are added to improve RF transmission characteristics, then signal bandwidth and impedance control improve, but device complexity increases
Solution Approach 1:
The via structure in the patent serves multiple functions simultaneously: it provides electrical connection, controls impedance, and minimizes parasitic effects. The conductive ring and multi-portion design achieve impedance control and parasitic reduction without requiring separate additional components, thereby maintaining device simplicity while improving RF performance
Data Source
AI summary
A multilayer circuit board having a central conductor and core layers between a first set of alternating layers and a second set of alternating layers. The central conductor includes a first compound via through the first set of alternating layers, and a second compound via through the second set of alternating layers. A gap extends from a first side of the multilayer circuit board to a second side of the multilayer circuit board. A first array of ground protrusions surrounds the gap and is arranged in a first pattern on the first side of the multilayer circuit board. A second array of ground protrusions surrounds the gap and is arranged in a second pattern on the second side of the multilayer circuit board. A ground path connects the first array of ground protrusions to the second array of ground protrusions.