MmWave Phased Array PCB Microvia Layout for Power Integrity
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Solution Overview
Problem
5G mmWave antennas face challenges in manufacturing due to high heat and high current requirements, which affect the accuracy of PCB etching and current carrying capacity, particularly in maximizing aperture while minimizing size and cost, and the use of plated through hole vias does not adequately address these issues.
Innovation Solution
A mmWave phased array antenna design featuring a PCB structure with multiple layers, including thick and thin copper power layers, where microvias are used to electrically couple the layers, with varying densities to optimize copper distribution and reduce footprint, and increase mechanical support and thermal robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If heavier copper weight is used to increase current carrying capacity, then the current carrying capacity is improved, but the accuracy of PCB etching levels deteriorates
Solution Approach 1:
The patent applies different copper weights (2 oz and 0.5 oz) to different regions of the PCB based on local current density requirements. High current areas such as power layers connected to beamforming ICs use 2 oz copper, while RF signal layers use 0.5 oz copper. This localized differentiation allows the design to meet current carrying requirements in critical areas without subjecting the entire PCB to heavy copper processing, thereby maintaining etching accuracy across all layers.
2Quantity of substance
If more copper is added to support high current ASIC requirements, then the current carrying capacity is improved, but the PCB surface area increases
Solution Approach 1:
The patent transitions from planar copper distribution to three-dimensional copper architecture by implementing multiple power layers (Layer 1 and Layer 3) with vertical interconnections via vias. This stacking approach allows high current paths to extend in the Z-dimension rather than requiring expanded surface area. The via structures provide vertical current pathways that connect thick copper power layers, enabling high current capacity within a compact footprint while preserving aperture space for antenna elements.
3Ease of manufacture
If plated through hole vias are used to interconnect layers, then the interconnect function is achieved, but the copper distribution remains constant and does not adequately address high current requirements
Solution Approach 1:
The patent changes the copper weight parameter from uniform to variable across different layers. Specifically, Layer 1 and Layer 3 are fabricated with 2 oz copper to handle high current, while Layer 2 uses 0.5 oz copper for RF signals. The via structures are strategically positioned to connect the heavy copper power layers, creating high-current pathways that leverage the increased copper cross-section. This parameter variation in copper weight enables optimized current distribution without requiring uniform heavy copper throughout the entire PCB.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances the current carrying capacity and thermal stability of the PCB, improving the accuracy of RF components and reducing the risk of copper delamination, thereby supporting high-performance mmWave frequencies while maintaining cost-effectiveness and minimizing size.
Implementation Method 1
A plurality of microvias extend through the first prepreg layer that electrically couple the thick copper layer to the signal layer and a plurality of microvias extend through the second prepreg layer that electrically couple the thin copper layer to the signal layer
Data Source
AI summary
A mmWave antenna that has particular application to be used in a 5G radio. The antenna includes a thick copper power layer, a first prepreg layer formed on one side of the thick power layer, a signal layer formed on a side of the first prepreg layer opposite to the thick power layer, a second prepreg layer formed on a side of the signal layer opposite to the first prepreg layer and a thin copper power layer formed on a side of second prepreg layer opposite to the signal layer. Microvias extend through the first prepreg layer that electrically couple the thick copper layer to the signal layer and microvias extend through the second prepreg layer that electrically couple the thin copper layer to the signal layer, where the number of microvias extending through the first prepreg layer is less than the number of microvias extending through the second prepreg layer.