Palladium Braze for Ceramic-Titanium Hermetic Seals
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Solution Overview
Problem
Hermetic sealing of implantable medical devices with composite housings made of dissimilar materials like titanium and ceramic is challenging due to differences in mechanical properties and thermal expansion coefficients, requiring a strong and efficient bonding method.
Innovation Solution
A palladium interface layer is used between titanium and ceramic parts, pressed together under pressure in an inert gas environment and heated to form a eutectic bond, creating a strong and hermetic seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hermetic seal is formed between titanium and ceramic parts using conventional bonding methods, then the structural integrity may be maintained, but the bonding strength and hermetic reliability are insufficient due to differences in mechanical properties and thermal expansion coefficients
Solution Approach 1:
A palladium interlayer is introduced between the titanium and ceramic parts to serve as a bonding intermediary. The palladium layer facilitates hermetic sealing by bonding to both materials, resolving the incompatibility between titanium and ceramic through a intermediate substance that accommodates their different mechanical and thermal properties.
Solution Approach 2:
The bonding structure becomes a composite of three materials: titanium, palladium, and ceramic. This composite approach allows each material to contribute its beneficial properties while the palladium interlayer ensures hermetic bonding despite the inherent differences between the dissimilar materials.
2Use of energy by moving object
If a non-metallic housing is used to improve RF power transmission efficiency, then the magnetic inductance between internal and external antennas is improved, but the hermetic sealing becomes more difficult due to the need to seal metal electrode contacts to the non-metallic housing
Solution Approach 1:
The palladium interlayer acts as a mediator between the metal electrode contacts and the non-metallic ceramic housing, enabling hermetic sealing of the composite housing structure that allows for efficient RF power transmission while maintaining the necessary hermetic barrier.
3Ease of manufacture
If titanium and ceramic parts are bonded directly without an interlayer, then the manufacturing process is simpler, but the bonding interface cannot provide a strong hermetic seal due to incompatible material properties
Solution Approach 1:
The palladium interlayer, while adding a step to the manufacturing process, enables precise hermetic sealing that cannot be achieved through direct bonding. The interlayer accommodates the material property differences and creates a reliable hermetic barrier at the interface.
Data Source
AI summary
A component assembly for use in living tissue comprises: a ceramic part; a metal part, e.g., a titanium metal; and a palladium (Pd) interlayer for bonding said ceramic part to the metal part. By applying sufficient heat to liquify a palladium-titanium interface, the Pd interlayer is used to braze the ceramic part to the titanium part to yield a hermetic seal.