Tuning Structure Mitigates Capacitive Discontinuity in Thick IC Package Cores
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Solution Overview
Problem
Integrated circuit (IC) package designs face challenges in signal transmission due to high capacitance and inductance in the core, leading to signal roll-off and resonance issues, particularly at higher frequencies, which affect the quality of high-speed signal transmission.
Innovation Solution
A tuning structure is introduced, comprising an electrical conductor extending along the outer perimeter of the core via cap, adjusting the angle θ to mitigate impedance changes, ripple magnitude, and return loss, thereby compensating for capacitive discontinuities and improving signal transmission through the IC package core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thicker package cores are used to meet mechanical requirements and provide better co-planarity for larger IC dice, then package strength and co-planarity are improved, but signal transmission quality deteriorates due to high capacitance and inductance causing roll-off and resonance at high frequencies
Solution Approach 1:
The patent introduces tuning structures (intermediary elements) between the core via caps and the differential core vias. These tuning structures act as mediators to compensate for the capacitive discontinuities caused by the thick core, allowing the package to maintain both mechanical strength and high-frequency signal transmission quality by抵消ing the adverse electrical effects of the thick core structure
Solution Approach 2:
The patent modifies the electrical parameters of the transmission path by adding tuning structures with specific inductance and capacitance values. By changing the electrical characteristics (adding series inductance and adjusting capacitance) of the via structure, the resonance frequency is shifted and signal quality is maintained despite the thick core geometry
2Stability of the object's composition
If thicker package cores are used to support larger IC dice, then mechanical stability is improved, but signal transmission speed and quality worsen due to increased capacitance and inductance
Solution Approach 1:
Tuning structures are introduced as intermediary elements that compensate for the electrical delays and signal degradation caused by the thick core, enabling high-speed signal transmission while maintaining the mechanically stable thick core structure
Solution Approach 2:
The tuning structures are designed to preemptively counteract the capacitive and inductive effects before they can degrade the signal. By placing these compensating elements at strategic locations (at the core via caps), the adverse effects of the thick core on signal speed are neutralized before they impact transmission performance
3Ease of manufacture
If standard core via structures are used in thick cores, then manufacturing simplicity is maintained, but signal transmission suffers from resonance dropout and high insertion loss at frequencies above 50 GHz
Solution Approach 1:
The tuning structures serve as intermediary components that can be integrated into the existing via fabrication process. These structures mediate between the simple via hole formation and the need for high-frequency performance, adding minimal manufacturing complexity while dramatically improving signal transmission reliability at high frequencies
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 tuning structure significantly reduces insertion loss and reflections at high frequencies, pushing the transition resonance above 50 GHz and enhancing overall signal quality, potentially simplifying serialization/deserialization processes with lower power consumption.
Implementation Method 1
The resonance dropout frequency is roughly inversely proportional to the core thickness and becomes of interest when the resonance dropout frequency drops below 50 GHz with a core thickness around 1.2 mm. This is partially due to the high capacitance between the differential core vias that pass through the core, the high dielectric constant of the core material, and a high capacitance associated with the via caps of the core layers
Implementation Method 2
This produces a roll-off in signal transmission and rising reflections with higher frequency. A resonance also exists within the core via structure caused by the inherent inductance of the core vias and distributed capacitance of the core via, along with the capacitance of the core via caps
Data Source
AI summary
A tuning structure to mitigate a capacitive discontinuity in an integrated circuit (IC) package includes an electrical conductor having a first end, a second end, and a conductor body between the first end and the second end. The first end is electrically coupled to a signal via, and the second end electrically coupled to an IC package core via cap. The electrical conductor is disposed substantially coplanar with the core via cap, and the conductor body is disposed along an outer perimeter of the core via cap. The second end is coupled to the via cap at a contact location. The contact location is determined based on a measurement of a performance metric associated with the transmission path through the IC package core, the core via cap, the electrical conductor, and the signal via.