Composite Feedthrough for AIMD EMI Mitigation

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Solution Overview

Problem

Hermetic terminal subassemblies for implantable medical devices face challenges in maintaining biocompatibility and resistance to degradation under applied bias current or voltage, while also addressing electromagnetic interference (EMI) and MRI-induced RF currents, which can lead to device malfunction and tissue damage.

Innovation Solution

A hermetically sealed feedthrough subassembly is designed with a composite conductor comprising a biocompatible metallic wire on the body fluid side and a lower-cost metallic wire on the device side, integrated within a ceramic insulator, along with a feedthrough capacitor to divert high-frequency signals and reduce EMI, and a gold braze for hermetic sealing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a hermetic terminal uses biocompatible materials and hermetic sealing to prevent body fluid ingress, then reliability is improved, but device complexity increases due to multiple material interfaces and sealing requirements

Engineering Contradiction:

ImprovehermeticityVSAvoidstructure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the hermetic seal and electrical connection functions into a single integrated structure. The conductive lead is directly brazed to the ferrule within the insulator body, merging the sealing function (braze joint) and electrical connection function (conductive pathway) into one component assembly, reducing the number of separate parts and interfaces.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent employs composite material construction with a ferrule, insulator body, and conductive lead made from different materials (metal, ceramic, and conductive material respectively). This composite structure allows each material to be optimized for its specific function while being joined through controlled interfaces that maintain hermeticity.

Inventive Principle:

Principle #40Composite materials

2Reliability

If conductive leadwires are used to connect therapy delivery leads, then electrical connectivity is improved, but electromagnetic interference (EMI) penetration increases causing device malfunction

Engineering Contradiction:

Improveelectrical connectivityVSAvoidEMI

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The insulator body acts as an intermediary element between the ferrule and the conductive lead. This ceramic insulator provides electrical isolation and filtering properties that block high-frequency EMI signals while allowing the hermetic seal and electrical connection to be maintained through the braze joint at the ferrule interface.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If therapy delivery leads are used for electrical signal transmission, then functionality is improved, but MRI-induced RF current heating occurs causing tissue damage

Engineering Contradiction:

Improvedevice functionalityVSAvoidRF current heating

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The insulator body and ferrule assembly serve as intermediary structures that provide controlled impedance matching and signal filtering. These components help manage RF current distribution during MRI procedures, reducing concentrated heating at lead interfaces while maintaining the device's therapeutic functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 provides a cost-effective, biocompatible, and reliable hermetic seal that minimizes the risk of device malfunction due to EMI and MRI-induced heating, while ensuring the structural integrity and longevity of the implantable medical device.

Implementation Method 1

a gold braze hermetically sealing the insulator body to the ferrule

Methodology Applied

Scientific EffectBrazing: Brazing

Implementation Method 2

a feedthrough capacitor to divert high-frequency signals and reduce EMI

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 3

a composite conductor comprising a biocompatible metallic wire on the body fluid side and a lower-cost metallic wire on the device side

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS10589107B2Circuit board mounted filtered feedthrough assembly having a composite conductive lead for an AIMD

Publication Date: 2020.03.17 GREATBATCH LTD

AI summary

A feedthrough separates a body fluid side from a device side. A passageway is disposed through the feedthrough. A body fluid side leadwire extends from a first end disposed inside the passageway to a second end on the body fluid side. A device side leadwire extends from a first end disposed inside the passageway to a second end on the device side. The body fluid side leadwire is hermetically sealed to the feedthrough body and is not of the same material as the device side leadwire. A circuit board has an active via hole with a second end of the second leadwire residing therein. The circuit board has an active circuit trace that is electrically connectable to electronic circuits housed in an AIMD, and a circuit board ground metallization. An active electrical path extends from the first leadwire to the second leadwire to an MLCC chip capacitor mounted on the circuit board and to the circuit board active circuit trace, and a ground electrical path extends from the MLCC chip capacitor to the circuit board ground metallization and then to the ferrule.