Feedthrough Assembly Capacitive Filter EMI Grounding

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Solution Overview

Problem

Implantable medical devices (IMDs) face interference from electromagnetic signals due to stray electromagnetic interference (EMI) conducted through lead conductors, which can disrupt the normal operation of IMD circuitry, and existing solutions do not adequately address this issue.

Innovation Solution

The use of feedthrough assemblies that incorporate a capacitive filter array and a ferrule, where the feedthrough ground conductive via is electrically coupled to the capacitive filter array ground conductive pathway, providing a hermetic seal and grounding EMI signals, thereby filtering out high-frequency electromagnetic interference while allowing low-frequency signals to pass through.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If lead conductors are used to connect IMD circuitry to external electrodes, then electrical connections can be established, but electromagnetic interference can be conducted through the lead conductors disrupting IMD operation

Engineering Contradiction:

ImproveIMD operation reliabilityVSAvoidelectromagnetic interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A feedthrough assembly serves as an intermediary component between the lead conductor and IMD circuitry. The feedthrough includes a capacitive filter that mediates the electrical connection while blocking high-frequency electromagnetic interference signals from reaching the sensitive IMD circuitry, thus protecting the system while maintaining electrical connectivity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The capacitive filter in the feedthrough assembly converts the harmful high-frequency electromagnetic interference into a beneficial filtering action. By using capacitors with appropriate time constants, the filter allows desired low-frequency physiological signals to pass while redirecting harmful high-frequency EMI signals to ground, effectively transforming the interference problem into a signal purification solution

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Object-affected harmful factors

If feedthrough assemblies with capacitive filter arrays are used to filter electromagnetic interference, then high-frequency signals are blocked, but the assembly complexity increases

Engineering Contradiction:

Improveelectromagnetic interferenceVSAvoidfeedthrough assembly complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The feedthrough assembly is segmented into distinct functional components: a ferrule for mechanical support and hermetic sealing, a feedthrough substrate with conductive vias for electrical pathways, and a capacitive filter array with multiple capacitors having different time constants. This segmentation allows each component to be optimized independently and facilitates modular manufacturing and assembly

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The feedthrough assembly performs multiple functions simultaneously: it provides hermetic sealing to protect IMD circuitry from bodily fluids, establishes electrical connections between leads and circuitry, and filters electromagnetic interference across multiple frequency ranges. The ferrule, substrate, and capacitive array work together to achieve these diverse functions in a single integrated component

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution effectively reduces electromagnetic interference, ensuring the reliable operation of IMDs by grounding high-frequency signals and maintaining the integrity of low-frequency signals, thus enhancing the performance and stability of IMDs.

Implementation Method 1

The feedthrough assemblies may be filtered feedthrough assemblies, and may include at least one capacitive filter and/or a capacitive filter array

Methodology Applied

Scientific EffectCapacitive filtering: Capacitance

Implementation Method 2

Implantable medical devices (IMDs) face interference from electromagnetic signals due to stray electromagnetic interference (EMI) conducted through lead conductors

Methodology Applied

Scientific EffectElectromagnetic interference: Electromagnetic Induction

Implementation Method 3

The feedthrough ground conductive via may be electrically coupled to a capacitive filter array ground conductive pathway. The feedthrough ground conductive via also may be electrically coupled to the ferrule.

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS8644936B2Feedthrough assembly including electrical ground through feedthrough substrate

Publication Date: 2014.02.04 MEDTRONIC INC

AI summary

A feedthrough assembly may include a ferrule defining a ferrule opening, a capacitive filter array at least partially disposed within the ferrule opening, and a feedthrough at least partially disposed within the ferrule opening. In some examples, the capacitive filter array includes a filter array ground conductive pathway. In some examples, the feedthrough includes a feedthrough ground conductive via. The feedthrough ground conductive via may be electrically coupled to the filter array ground conductive pathway, and the feedthrough ground conductive via may be electrically coupled to the ferrule.