Package Substrate Air Gaps for Low-Loss High-Speed Interconnects
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Solution Overview
Problem
Current package substrates face challenges in minimizing signal loss and parasitic capacitance at high data rates due to limitations in dielectric and conductor materials, particularly for high-speed signals above 10 GHz, where traditional copper voids and dielectric materials reach their limits in reducing insertion loss and maintaining structural reliability.
Innovation Solution
Incorporation of air gap structures within the package substrate, specifically between and around stripline traces, to reduce the effective dielectric constant and parasitic capacitance, while ensuring structural integrity by exposing these air gaps on the surface and extending them orthogonally into the organic dielectric material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional copper voids and dielectric materials are used, then structural reliability is maintained, but signal loss and parasitic capacitance increase at high data rates
Solution Approach 1:
The patent changes the dielectric constant parameter by introducing air gap structures (effective dielectric constant reduction) around stripline traces. This parameter change reduces parasitic capacitance and signal loss at high frequencies while maintaining structural integrity through the controlled air gap geometry and material selection.
Solution Approach 2:
The patent creates a composite structure combining organic dielectric material and air gaps in a layered configuration. This composite approach allows the air gaps to reduce parasitic capacitance while the organic dielectric material maintains structural reliability, achieving both goals simultaneously.
2Speed
If air gap structures are introduced to reduce parasitic capacitance, then bandwidth increases, but manufacturing complexity increases
Solution Approach 1:
The patent segments the dielectric material by introducing discrete air gap structures at specific locations around stripline traces. This segmentation reduces parasitic capacitance where needed while maintaining solid dielectric support elsewhere, balancing bandwidth improvement with manufacturing feasibility.
Solution Approach 2:
The air gap structures act as intermediary elements between the stripline traces and the organic dielectric material. These intermediaries reduce direct capacitive coupling and parasitic effects while allowing the manufacturing process to proceed through standardized layers and materials.
3Reliability
If air gap structures are used to reduce insertion loss, then signal integrity improves, but dielectric material usage decreases
Solution Approach 1:
The patent applies local quality by introducing air gaps only in specific regions around stripline traces where parasitic capacitance and signal loss are most problematic. This localized approach improves signal integrity where needed while minimizing the overall reduction of dielectric material, maintaining structural support in other areas.
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
The air gap structures effectively decrease insertion loss by up to 25% and reduce parasitic capacitance, enhancing the bandwidth and reliability of high-speed interconnects without compromising the structural reliability of the package substrate.
Implementation Method 1
reduce the effective dielectric constant and parasitic capacitance
Data Source
AI summary
Embodiments of a microelectronic assembly that includes: a package substrate, comprising buildup layers of an organic dielectric material and a plurality of layers of conductive traces in the organic dielectric material, the package substrate having a first surface and a second surface opposite the first surface; and a plurality of integrated circuit (IC) dies coupled to the package substrate on the first side. The plurality of layers of conductive traces comprises a pair of stripline traces or microstrips in one of the layers, the stripline traces or microstrips are surrounded by air gap structures in the organic dielectric material, and the air gap structures are exposed on the first surface.