Flip-Chip Microstrip MMICs With Conductive Vias

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Solution Overview

Problem

Flip-chip mounted Coplanar Waveguide (CPW) Monolithic Microwave Integrated Circuits (MMICs) are more difficult to design and exhibit degraded performance compared to microstrip MMICs, especially at higher frequencies, making microstrip MMICs more preferable due to their availability, cost-effectiveness, and performance.

Innovation Solution

A microstrip MMIC chip is flip-chip mounted to a printed circuit board with conductive vias connecting the ground plane of the MMIC chip to the board's ground conductor, enabling direct mounting without ribbon or wire bonds and maintaining thermal and electrical interfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If flip-chip mounted CPW MMICs are used, then direct mounting without ribbon or wire bonds is enabled, but design difficulty increases and performance degrades at higher frequencies

Engineering Contradiction:

Improvedirect mounting capabilityVSAvoiddesign difficulty

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent inverts the conventional microstrip configuration by placing the ground plane on the front surface instead of the back surface, and using conductive vias to connect the ground plane to the PCB ground. This inversion enables flip-chip mounting while maintaining microstrip performance characteristics, resolving the contradiction between direct mounting capability and design complexity.

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of operation

If flip-chip mounted CPW MMICs are used, then direct mounting without ribbon or wire bonds is enabled, but performance degrades at higher frequencies

Engineering Contradiction:

Improvedirect mounting capabilityVSAvoidperformance at higher frequencies

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

By inverting the conventional configuration and using a ground plane on the front surface with conductive via connections, the patent maintains controlled impedance and signal integrity at higher frequencies while enabling direct flip-chip mounting, thus improving high-frequency performance compared to traditional CPW designs.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent replaces the mechanical ribbon or wire bond connections with direct flip-chip solder connections through conductive vias, eliminating the mechanical intermediate structures that limit high-frequency performance and enabling direct mounting while maintaining electrical integrity at higher frequencies.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If traditional microstrip configuration is used, then performance is maintained at higher frequencies, but thermal interface cannot be separated from electrical ground

Engineering Contradiction:

Improveperformance at higher frequenciesVSAvoidthermal interface separation

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent segments the thermal and electrical ground paths by using conductive vias to connect the ground plane to the PCB ground, allowing the thermal interface to be separated from the electrical ground connection. This enables independent optimization of thermal management and electrical performance, resolving the contradiction between high-frequency performance and thermal interface separation.

Inventive Principle:

Principle #1Segmentation

4Ease of manufacture

If microstrip MMICs are used instead of CPW MMICs, then cost is reduced and availability improved, but direct flip-chip mounting is not typically supported

Engineering Contradiction:

Improvecost and availabilityVSAvoiddirect mounting capability

Core Design Contradiction:

Ease of manufactureVSEase of operation

Solution Approach 1:

The patent adapts the microstrip design (which is more readily available and cost-effective) by inverting the configuration to include a front-surface ground plane with conductive via connections, enabling direct flip-chip mounting while maintaining the cost and availability advantages of microstrip MMICs.

Inventive Principle:

Principle #13The other way round (Inversion)

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 configuration enhances the performance of microstrip MMICs by ensuring effective electrical and thermal connections, improving their performance at higher frequencies and reducing design complexity, while maintaining cost-effectiveness.

Implementation Method 1

a conductive via passing through the substrate electrically interconnecting the ground region conductor and the ground plane conductor

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

the strip conductor and the ground plane conductor providing a microstrip transmission line to the active device

Methodology Applied

Scientific EffectElectromagnetic wave propagation: Electromagnetic Induction

Implementation Method 3

Separating the thermal interface from all electrical interfaces (including the electrical ground) enables the chip to be mounted directly on a printed circuit board

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS8866291B2Flip-chip mounted microstrip monolithic microwave integrated circuits (MMICs)

Publication Date: 2014.10.21 RAYTHEON CO

AI summary

A microstrip MMIC chip flip-chip mounted to a printed circuit board with conductive vias passing through the chip to electrical connect a ground plane of the microstrip MMIC chip to a ground conductor of the printed circuit board.