Hermetic Micro-Cavity for MMIC Protection

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Solution Overview

Problem

Conformal coatings and encapsulants with high dielectric constants degrade the performance of monolithic microwave integrated circuits (MMICs) and fail to provide adequate protection against environmental contaminants in non-hermetic applications.

Innovation Solution

A hermetically sealed micro-cavity architecture is created using a water-impermeable substrate, a dielectric encapsulant, a capping layer of polymer, and a barrier layer, where the barrier layer is formed from inorganic materials or their composites, effectively preventing water and gas penetration and maintaining the performance and reliability of sensitive electronic circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conformal coatings and encapsulants are applied to protect electronic circuits, then protection from environmental contaminants is provided, but dielectric performance degrades due to high dielectric constant and loss tangent

Engineering Contradiction:

Improveprotection from environmental contaminantsVSAvoiddielectric loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The encapsulation system is divided into multiple functional layers: a hermetic barrier layer (inorganic material) for environmental protection, a low-dielectric-constant encapsulant material for electrical performance, and a capping layer for sealing. This segmentation allows each layer to optimize its specific function without compromising overall performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite material structures, including hermetic barrier layers made from inorganic materials (metal oxides, nitrides, or carbides) combined with organic encapsulant materials. This composite approach provides both the protective hermetic seal and the low dielectric loss properties required for MMIC performance.

Inventive Principle:

Principle #40Composite materials

2Reliability

If barrier layers are added to provide hermetic protection, then protection from environmental contaminants is improved, but device complexity increases

Engineering Contradiction:

Improvehermetic protectionVSAvoidnumber of layers

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The hermetic barrier layer and encapsulant are integrated into a unified multi-layer structure where the barrier layer is deposited directly onto the substrate and circuit, and the encapsulant is applied over the barrier layer. This merging of functions into a single integrated assembly reduces manufacturing steps compared to separate protection systems.

Inventive Principle:

Principle #5Merging (Combining)

3Ease of manufacture

If polymeric encapsulants are used for coating, then ease of manufacture is improved, but dielectric performance decreases due to higher dielectric constant

Engineering Contradiction:

Improvecoating applicationVSAvoiddielectric loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

Different regions of the encapsulation system have different material properties optimized for their specific functions: the hermetic barrier layer uses inorganic materials with low dielectric constant for electrical performance, while the capping layer uses polymer materials for ease of application and sealing. This local optimization allows each material to excel at its intended function.

Inventive Principle:

Principle #3Local quality

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 significantly reduces water vapor transmission through the capping and barrier layers, achieving a hermetic seal that protects electronic circuits from corrosive effects and dielectric loading, thereby preserving performance and reliability while allowing for conformal coatings and underfills without degrading MMIC performance.

Implementation Method 1

the barrier layer, wherein the water impermeable substrate, the dielectric encapsulant, the capping layer, and the barrier layer form a hermetically sealed micro-cavity

Methodology Applied

Scientific EffectPermeation barrier:

Implementation Method 2

a dielectric encapsulant on the electronic circuit

Methodology Applied

Scientific EffectDielectric insulation: Dielectric

Implementation Method 3

a capping layer comprising a polymer on the dielectric encapsulant

Methodology Applied

Scientific EffectHermetic sealing:

Data Source

PatentUS11139164B2Electronic device including hermetic micro-cavity and methods of preparing the same

Publication Date: 2021.10.05 RAYTHEON CO

AI summary

An electronic device includes: a water impermeable substrate; at least one electronic circuit on the water impermeable substrate; a dielectric encapsulant on the electronic circuit; a capping layer comprising a polymer on the dielectric encapsulant; and a barrier layer on the capping layer, the water impermeable substrate, the dielectric encapsulant, the capping layer, and the barrier layer forming a hermetically sealed micro-cavity.