Feedthrough Terminal Mullion for EMI Filter Flashover Resistance
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Solution Overview
Problem
Active implantable medical devices (AIMDs) face interference from electromagnetic interference (EMI) due to leadwires acting as antennas, which can disrupt device operation, especially during diagnostic procedures like MRI and exposure to higher power emitters, and there is a need for improved filtering and immunity.
Innovation Solution
A feedthrough terminal assembly with a non-conductive mullion creating a tortuous path between terminal pins or leadwires and a conductive element, combined with a feedthrough filter capacitor, to increase resistance to arcing/flashover and enhance EMI filtering, using a disc-shaped mullion with apertures and convolutions to further increase creepage distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If leadwires are used to connect terminal pins for signal transmission, then electrical signals can be transmitted from exterior to interior, but the leadwires act as antennas to collect EMI signals causing interference
Solution Approach 1:
A feedthrough capacitor is introduced as an intermediary component between the terminal pin and the interior circuitry. The capacitor provides a low-impedance path to ground for EMI frequencies while maintaining signal transmission capability, effectively filtering out electromagnetic interference collected by the leadwires
Solution Approach 2:
The impedance characteristics of the feedthrough path are changed by incorporating a capacitor with specific capacitance values optimized for EMI frequencies. This creates frequency-dependent impedance where high-frequency EMI signals are shunted to ground while lower frequency medical signals pass through
2Device complexity
If a straight path is used between terminal pins for simplicity, then device complexity is reduced, but resistance to arcing/flashover is insufficient under high voltage conditions
Solution Approach 1:
A convoluted or serpentine path is used instead of a straight line, creating multiple bends and turns in the feedthrough route. This increases the creepage distance and surface path length between high-voltage points, making it more difficult for arcs to form while maintaining a relatively compact physical footprint
Solution Approach 2:
The feedthrough path is routed through three-dimensional space using multiple layers and vertical transitions rather than a simple planar path. This increases the effective creepage distance without proportionally increasing the device footprint, providing better flashover resistance in a compact form
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 increases the resistance to arcing/flashover and enhances EMI filtering, protecting AIMDs from interference, including higher power emitters and MRI, thereby ensuring reliable operation of medical devices.
Implementation Method 1
feedthrough capacitor for decoupling EMI signals in a manner preventing such unwanted signals from entering the housing
Implementation Method 2
feedthrough capacitor for decoupling EMI signals
Implementation Method 3
non-conductive mullion disposed relative to the terminal pin or leadwire for increasing creepage distance between the terminal pin or leadwire and another conductive element
Data Source
AI summary
A feedthrough terminal assembly for an active implantable medical device includes a conductive terminal pin or leadwire, a feedthrough filter capacitor having a first set of electrode plates conductively coupled to the terminal pin or leadwire, and a second set of electrode plates conductively coupled to a housing, ferrule or ground plane of the active implantable medical device, and a non-conductive mullion disposed relative to the terminal pin or leadwire for increasing creepage distance between the terminal pin or leadwire and another conductive element, creating a tortuous path that increases resistance to arcing/flashover.