Filtered Feedthrough Lead Frame Assembly for EMI-Safe IMDs
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Solution Overview
Problem
Implantable medical devices (IMDs) face interference from electromagnetic signals due to the conductive nature of lead conductors, which can disrupt the normal operation of the device's circuitry, and existing solutions do not adequately address this issue while maintaining a hermetic seal and ensuring biocompatibility.
Innovation Solution
The implementation of a capacitive filtered feedthrough array that includes a capacitive filter array and a lead frame assembly, which connects the feedthrough conductive pathways to the filter array conductive pathways, providing a filtered electrical connection while maintaining physical separation and a hermetic seal, using materials like silver-palladium alloy and glass frit for conductive paste and ceramic materials for the filter and feedthrough substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a feedthrough assembly is used to provide electrical connections in an implantable medical device, then electrical connectivity between interior and exterior of the housing is achieved, but the device becomes susceptible to electromagnetic interference through the lead conductors
Solution Approach 1:
A capacitive filter array is introduced as an intermediary component between the feedthrough and the lead conductors. The filter array includes capacitive elements that couple to the conductive pathways, serving as a mediator that blocks high-frequency electromagnetic interference while allowing low-frequency physiological signals to pass through to the circuitry.
Solution Approach 2:
The capacitive filter array converts the harmful electromagnetic interference into a beneficial filtering function. By strategically placing capacitive elements with appropriate capacitance values, the design transforms the EMI problem into an opportunity to enhance signal quality, where the same conductive pathways that transmit interference also carry the filtered physiological signals to the circuitry.
2Object-affected harmful factors
If a capacitive filter array is integrated into the feedthrough assembly, then electromagnetic interference is filtered, but the device complexity increases
Solution Approach 1:
The capacitive filter array is merged with the feedthrough assembly by integrating the capacitive elements directly into the conductive pathways of the feedthrough. This combination eliminates the need for separate filtering components and reduces the overall device complexity, as the filtering function is achieved within the existing structural framework of the feedthrough assembly.
Solution Approach 2:
The conductive pathways of the feedthrough assembly serve multiple functions: they provide electrical connectivity between the interior and exterior of the housing, and simultaneously serve as the conductive paths for the capacitive filter array to block electromagnetic interference. This multi-functionality reduces the need for additional components and simplifies the overall design.
3Reliability
If thick film conductive paste or lead frames are used for connections, then hermetic seal and biocompatibility are ensured, but manufacturing precision requirements increase
Solution Approach 1:
The design utilizes thick film conductive paste with specific material properties (viscosity, firing temperature, conductivity) to achieve reliable electrical connections while maintaining hermetic seal integrity. By carefully selecting and controlling these material parameters, the manufacturing process can accommodate normal tolerances without compromising connection quality or seal integrity.
Solution Approach 2:
The feedthrough assembly employs composite materials including thick film conductive paste applied to ceramic or glass substrates, and biocompatible lead frames with specific alloy compositions. These composite materials provide both the electrical conductivity needed for connections and the hermetic seal properties required for implantable devices, while their material characteristics facilitate manufacturing within standard precision tolerances.
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 filters out electromagnetic interference, ensuring the integrity of the IMD's operation by transmitting high-frequency signals to ground and low-frequency signals to the circuitry, while maintaining a hermetic seal and biocompatibility, thus preventing damage from bodily fluids and ensuring reliable device function.
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
Implementation Method 2
providing a filtered electrical connection that transmits low-frequency signals while grounding high-frequency electromagnetic interference
Data Source
AI summary
A feedthrough assembly may include a ferrule defining a ferrule opening, a feedthrough at least partially disposed within the ferrule opening, a capacitive filter array at least partially disposed within the ferrule opening, and a lead frame assembly. The feedthrough may include at least one feedthrough conductive pathway and the capacitive filter array may include at least one filter array conductive pathway. The lead frame assembly may include an electrically conductive lead electrically connecting the at least one feedthrough conductive pathway and the at least one filter array conductive pathway.