Package Substrate Layout for Power Loop Impedance Reduction
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Solution Overview
Problem
Conventional substrate configurations for integrated circuits result in high impedance and increased power noise due to the diversion of return current, which affects signal fidelity, particularly at higher frequencies.
Innovation Solution
A substrate layout featuring a ground plane with a trace rail along its periphery and perpendicular traces that couple to vias, allowing direct return current flow without interruption, thereby reducing impedance and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a trace is configured to connect power supply connections to the die area, then electrical connectivity is achieved, but the trace may cut off the direct return current path causing increased impedance
Solution Approach 1:
The substrate is divided into multiple layers with distinct functional assignments. The first layer contains the ground plane for the first power loop, while the second layer contains the power supply connections and trace configuration for the second power loop. This segmentation allows each layer to be optimized independently, enabling the trace to connect power supplies to the die without interfering with the return current path on the ground plane layer.
Solution Approach 2:
The solution moves the ground plane and return current path to a different spatial dimension (separate layer) from the power supply trace. By utilizing the vertical dimension through multiple substrate layers, the trace can provide power connectivity while the ground plane simultaneously provides an uninterrupted return current path, eliminating the impedance issue that would occur if both functions were constrained to the same plane.
2Reliability
If return current is diverted around a trace to avoid cutting off the direct path, then connectivity is maintained, but impedance increases and power noise increases
Solution Approach 1:
The power delivery network is segmented into separate functional layers: the first layer dedicated to the ground plane and return current path, and the second layer dedicated to power supply connections and traces. This segmentation ensures that the return current flows directly through the ground plane without being diverted by power traces, maintaining low impedance and reducing power noise that would degrade signal fidelity.
Solution Approach 2:
The ground plane on the first layer acts as an intermediary structure that provides a dedicated, low-impedance return current path. By introducing this intermediate ground plane layer between the power supply trace layer and the die, the return current is guided along an optimal path that does not intersect with power traces, thereby reducing electromagnetic interference and power noise.
Data Source
AI summary
In accordance with an embodiment, a method comprises providing a substrate having a conductive material thereon, forming a ground plane, a first trace rail, and a first perpendicular trace from the conductive material, and forming an insulator material over the ground plane, the first trace rail, and the first perpendicular trace. The ground plane is between the first trace rail and an area of the substrate over which will be a die. The first trace rail extends along a first outer edge of the ground plane, and the first perpendicular trace is coupled to the first trace rail and extends perpendicularly from the first trace rail.