Filtered Feedthrough Assembly with Gold Braze Seal
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Solution Overview
Problem
Hermetic terminal subassemblies for active implantable medical devices face challenges in maintaining hermeticity and resisting electromagnetic interference (EMI) due to material mismatch and stress issues, particularly with ceramic-to-metal interfaces, and the high cost and fragility of platinum-based leadwires.
Innovation Solution
A hermetically sealed filtered feedthrough assembly is created using a co-fired, essentially pure platinum fill within a monolithic alumina insulator substrate, with a gold braze sealing the insulator to the ferrule, and a capacitor with a dielectric constant less than 1000, minimizing stress and eliminating the need for expensive platinum-based leadwires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ceramic-to-metal interfaces are used in hermetic terminals, then hermeticity is achieved, but material mismatch and stress issues occur
Solution Approach 1:
The patent introduces a transition layer comprising a first metal layer and a second metal layer between the ceramic insulator and the ferrule. The first metal layer bonds to the ceramic insulator, while the second metal layer bonds to the ferrule, serving as an intermediary that resolves the material mismatch between ceramic and metal, thereby reducing stress while maintaining hermeticity.
2Reliability
If platinum-based leadwires are used, then hermeticity and biocompatibility are maintained, but cost increases and fragility occurs
Solution Approach 1:
The patent changes the material parameter of the leadwire from platinum to a non-precious metal alloy, and modifies the connection method by coating the leadwire with a metallization layer that bonds to the ferrule. This parameter change reduces cost and improves manufacturability while maintaining hermeticity through the coating layer and brazing process.
3Reliability
If traditional hermetic terminal structures are used, then electrical connections are established, but EMI filtering is insufficient
Solution Approach 1:
The patent merges the hermetic terminal function with the EMI filtering function into a single integrated structure. The capacitor is formed using the ferrule as one electrode and a ground electrode as the other, with the insulator as the dielectric, combining electrical connection and EMI filtering in one component.
4Reliability
If complex multi-layer metal coatings are applied to ceramic insulators, then hermetic sealing is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies different metal layers with specific properties at different locations on the ceramic insulator surface. The first metal layer is applied to the region bonding with the ferrule, while the second metal layer is applied to the region bonding with the capacitor electrode, optimizing each region's bonding characteristics without requiring complex multi-layer coatings everywhere.
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 robust, cost-effective, and reliable hermetic seal that minimizes stress and maintains hermeticity over the device's service life, while also effectively filtering EMI and reducing the risk of leadwire fracture.
Implementation Method 1
an electrically conductive fill (186) disposed within and hermetically sealing the at least one via hole, wherein the electrically conductive fill and the insulator are co-fired
Implementation Method 2
a gold braze (140) hermetically sealing the insulator to the ferrule
Implementation Method 3
At least one capacitor (124,194) is disposed on the device side, which comprises: i) a capacitor dielectric body (154); ii) at least one active electrode plate (134) and at least one ground electrode plate (136) disposed within the capacitor dielectric body (154)
Data Source
AI summary
A hermetically sealed filtered feedthrough assembly attachable to an AIMD includes an insulator hermetically sealing the opening of a ferrule with a gold braze. The ferrule includes a peninsula extending into the ferrule opening and the insulator has a cutout matching the peninsula. A sintered platinum-containing paste hermetically seals at least one via hole extending through the insulator. At least one capacitor is disposed on the device side. An active electrical connection electrically connects the capacitor active metallization to the sintered paste. A ground electrical connection electrically connects the capacitor ground metallization disposed within a capacitor ground passageway to the portion of the gold braze along the ferrule peninsula. The dielectric of the capacitor may be less than 1,000 k.