Titanium Hermetic Feedthrough Assembly for Low-Heat Glass Sealing
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Solution Overview
Problem
The challenge in creating reliable electrical connections for lithium batteries in implantable medical devices (IMDs) lies in the high thermal expansion coefficient of molybdenum pins, which requires high-temperature welding, potentially damaging the glass insulator and other components, and existing hermetic feedthrough assemblies do not provide sufficient reliability or biocompatibility for long-term IMD operation.
Innovation Solution
A hermetic feedthrough assembly is developed using a titanium ferrule and inner conductor with a low silica or silica-free insulating core, where the coefficient of thermal expansion of the inner conductor is equal to or greater than the insulating core, forming a molecular bond to create a reliable seal, reducing the need for high-temperature welding and enhancing biocompatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If molybdenum pins are used in the feedthrough assembly, then electrical conductivity and corrosion resistance are improved, but the high melting temperature requires high-temperature welding that may damage the glass insulator
Solution Approach 1:
The patent changes the material parameter of the pin from molybdenum to titanium, which has a lower melting temperature and better weldability. This parameter change allows joining operations to be performed at lower temperatures that do not damage the glass insulator, while still achieving reliable electrical connections through the titanium material's inherent conductivity
Solution Approach 2:
The patent employs a composite structure where the titanium pin is molecularly bonded to the glass insulator. This composite approach combines the electrical conductivity and biocompatibility of titanium with the insulating and sealing properties of the glass, creating a integrated assembly that achieves reliable electrical connections without requiring high-temperature welding that would damage the glass
2Reliability
If high-temperature welding is used to join molybdenum pins, then electrical connections are established, but the glass insulator and other components may be damaged
Solution Approach 1:
The patent changes the joining process parameter from high-temperature welding to lower-temperature molecular bonding. This parameter change in the joining process allows the glass insulator and other components to remain intact during assembly, while still achieving reliable electrical connections through the titanium pin's properties and its molecular bond to the glass
Solution Approach 2:
The patent replaces the mechanical/thermal welding process with a molecular bonding process. Instead of using high-temperature welding to join the pin to the glass insulator, the titanium pin forms a molecular bond with the glass through chemical affinity, achieving a strong, reliable connection at lower temperatures that preserves component integrity
3Reliability
If conventional hermetic feedthrough assemblies are used, then hermetic sealing is achieved, but sufficient reliability and biocompatibility for long-term IMD operation are not provided
Solution Approach 1:
The patent employs a composite structure where the titanium pin is molecularly bonded to the glass insulator. This composite approach combines the electrical conductivity and biocompatibility of titanium with the insulating and sealing properties of the glass, creating an integrated assembly that achieves reliable electrical connections without requiring high-temperature welding that would damage the glass
Solution Approach 2:
The patent changes the material parameter of the pin from molybdenum to titanium, which has a lower melting temperature and better weldability. This parameter change allows joining operations to be performed at lower temperatures that do not damage the glass insulator, while still achieving reliable electrical connections through the titanium material's inherent conductivity
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 provides more reliable electrical connections and avoids damage to components during joining operations, ensuring the long-term reliability and biocompatibility of IMDs by using a titanium-based feedthrough assembly with a molecularly bonded seal.
Implementation Method 1
the first and second compositions are molecularly bonded with one another to form a hermetic seal between the inner conductor and the insulating core
Implementation Method 2
The first CTE of the inner conductor is equal to or greater than the second CTE of the insulating core
Data Source
AI summary
A feedthrough assembly for an implantable medical device includes a ferrule, an inner conductor, and an insulating core. The ferrule has a lumen. The inner conductor extends through the lumen of the ferrule. The inner conductor has a first material composition. The insulating core is disposed within the lumen of the ferrule and separates the inner conductor from the ferrule. The insulating core has a second material composition that is different from the first material composition of the inner conductor. A coefficient of thermal expansion (CTE) of the inner conductor is no less than the CTE of the insulating core. The inner conductor is bonded to the insulating core to form a glass-to-metal seal between the inner conductor and the insulating core.