Flip-Chip IC Package Substrate Trace Inductance Termination
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Solution Overview
Problem
High-speed integrated circuits (ICs) packaged using flip-chip techniques experience significant reflections due to impedance mismatches, leading to poor return loss, especially when the IC does not provide a good termination, which can result in data transfer errors.
Innovation Solution
A package substrate with a trace that includes a first portion with a characteristic impedance and a second, high-inductance portion proximate to the IC, which operates in cooperation with the capacitance of the IC's port to reduce return loss by providing a selected inductance and termination impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flip-chip packaging is used for high-speed ICs, then connection density and electrical performance are improved, but impedance mismatches cause significant reflections and poor return loss
Solution Approach 1:
A high-inductance trace portion is introduced as an intermediary element between the IC port and the standard impedance trace. This intermediary provides a selected inductance that, when combined with the port capacitance, creates a termination impedance matching the system characteristic impedance, thereby reducing reflections and improving return loss while maintaining the flip-chip packaging benefits
2Device complexity
If the IC does not provide good termination, then device complexity is reduced, but return loss deteriorates significantly
Solution Approach 1:
The package substrate trace with high-inductance portion serves as a termination-matching intermediary that compensates for the IC's inadequate termination. The high-inductance section, when combined with the IC port capacitance, creates the necessary impedance match to the system characteristic impedance, reducing reflections without requiring changes to the IC itself
Solution Approach 2:
The trace impedance is changed along its length, with a standard characteristic impedance portion for signal transmission and a high-inductance portion with different electrical characteristics for termination matching. This parameter change allows the same trace to serve dual functions: signal carrying and impedance matching
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 solution effectively reduces return loss from the high-speed port, improving data transfer reliability by ensuring a termination impedance closer to the system's characteristic impedance, thereby minimizing reflections and errors.
Implementation Method 1
A trace in the package substrate includes a first portion and a second, high-inductance, portion. The high-inductance portion of the trace is proximate to a port of the integrated circuit and provides a selected inductance operating in cooperation with the capacitance of the port to reduce return loss from the port.
Implementation Method 2
The high-inductance portion of the trace is proximate to a port of the integrated circuit and provides a selected inductance operating in cooperation with the capacitance of the port to reduce return loss from the port.
Data Source
AI summary
A packaged integrated circuit includes an integrated circuit and a package substrate. A trace in the package substrate includes a first portion and a second, high-inductance, portion. The high-inductance portion of the trace is proximate to a port of the integrated circuit and provides a selected inductance operating in cooperation with the capacitance of the port to reduce return loss from the port. The first portion of the trace is part of a transmission line having a characteristic impedance.