Low Impedance Oxide Resistant Feedthrough Capacitor
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Solution Overview
Problem
Existing feedthrough capacitors in active implantable medical devices face challenges with high-frequency performance due to titanium oxide formation, which increases equivalent series resistance and degrades performance, and the use of gold braze for attachment is expensive and inefficient.
Innovation Solution
A hermetically sealed filtered feedthrough assembly with a low impedance electrical connection using an oxide-resistant metal addition, such as gold, platinum, or palladium, directly attached to the ferrule or housing, providing a reliable grounding path for the feedthrough capacitor, reducing oxide-related resistance and improving high-frequency performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the feedthrough capacitor ground plates are directly connected to the titanium ferrule, then the grounding path is simple and direct, but titanium oxide formation increases the equivalent series resistance and degrades high-frequency performance
Solution Approach 1:
The patent introduces an intermediate oxide-resistant metal layer (such as ruthenium, osmium, or iridium) between the titanium ferrule and the feedthrough capacitor ground plates. This intermediary layer prevents oxide formation at the critical electrical contact interface, thereby maintaining low equivalent series resistance and ensuring reliable high-frequency performance while keeping the grounding path structure relatively simple.
2Reliability
If gold braze material is used to form the hermetic seal between the alumina and titanium ferrule, then the hermetic seal is reliable and provides oxide resistance, but the cost increases significantly
Solution Approach 1:
The patent replaces expensive gold braze material with more cost-effective oxide-resistant metal layers (such as ruthenium, osmium, or iridium) that provide the necessary hermetic seal and oxide resistance functions. These alternative materials achieve the same reliability at lower cost, making the hermetic seal both effective and economically viable.
3Ease of manufacture
If the feedthrough capacitor is grounded directly to the titanium ferrule without oxide-resistant metal addition, then the manufacturing process is simple, but the equivalent series resistance increases due to oxide formation
Solution Approach 1:
The patent applies oxide-resistant metal layers (such as ruthenium, osmium, or iridium) to the titanium ferrule surface before assembling the feedthrough capacitor. This preliminary action ensures that the oxide-resistant property is already in place before the critical electrical connection is made, thereby guaranteeing low equivalent series resistance without complicating the subsequent manufacturing process.
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 achieves a low total resistance of less than 1 milliohm and total inductance of less than 10 nanohenries, enhancing the capacitors' performance by eliminating oxide-related degradation and reducing costs associated with gold braze usage.
Implementation Method 1
a second low impedance electrical connection between the second end metallization and the ferrule or housing. The second low impedance electrical connection includes an oxide-resistant metal addition attached directly to the ferrule or housing
Implementation Method 2
A hermetically sealed filtered feedthrough assembly with a low impedance electrical connection... intercept the EMI at the point of lead conductor ingress and egress to the AIMD
Data Source
AI summary
A hermetically sealed filtered feedthrough assembly for an AIMD includes an insulator hermetically sealed to a conductive ferrule or housing. A conductor is hermetically sealed and disposed through the insulator in non-conductive relation to the conductive ferrule or housing between a body fluid side and a device side. A feedthrough capacitor is disposed on the device side. A first low impedance electrical connection is between a first end metallization of the capacitor and the conductor. A second low impedance electrical connection is between a second end metallization of the capacitor and the ferrule or housing. The second low impedance electrical connection includes an oxide-resistant metal addition attached directly to the ferrule or housing and an electrical connection coupling the second end metallization electrically and physically directly to the oxide-resistant metal addition.