Ti-Pd Braze Interface for Ceramic-Titanium Hermetic Sealing
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Solution Overview
Problem
The challenge lies in hermetically sealing medical device housings that consist of dissimilar materials like titanium and ceramic, which have different mechanical properties, such as thermal coefficients of expansion, to ensure a strong and effective seal for implantable microstimulators that require non-metallic components for RF energy transmission and electrode contact integration.
Innovation Solution
A titanium-palladium (Ti-Pd) interface layer is used between the titanium and ceramic parts, pressed together in an inert gas environment and heated to create a eutectic bond, forming a strong and hermetic seal that is impervious to gases and water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a housing is made completely from metal (titanium), then the housing provides strong structural integrity and hermetic sealing, but metal acts as a shield against RF energy transmissions and prevents antenna operation
Solution Approach 1:
The housing is divided into two separate parts: a metal (titanium) portion and a non-metallic (ceramic) portion. The metal portion provides hermetic sealing and structural integrity, while the non-metallic portion allows RF energy transmission. This segmentation resolves the contradiction by assigning different functional requirements to different material sections of the same housing structure.
2Object-generated harmful factors
If a housing is made at least partly from non-metallic material (ceramic), then RF power transmissions are improved and magnetic inductance between internal and external antennas is enhanced, but hermetic sealing becomes more difficult to achieve
Solution Approach 1:
The housing is constructed as a composite structure combining metal and non-metallic materials. Specifically, a titanium portion is hermetically bonded to a ceramic portion using a titanium-palladium braze interface. This composite construction allows the housing to simultaneously achieve RF energy transmission (through the ceramic portion) and hermetic sealing (through the metal-ceramic bond), resolving the contradiction between material composition and sealing reliability.
3Reliability
If ceramic and titanium parts are brazed together, then a hermetic seal is achieved, but the different mechanical properties and thermal coefficients of expansion of the dissimilar materials create bonding challenges
Solution Approach 1:
A titanium-palladium (Ti-Pd) braze interface layer is introduced as an intermediary material between the titanium and ceramic parts. This intermediate layer facilitates hermetic bonding by being compatible with both dissimilar materials, accommodating their different mechanical properties and thermal coefficients of expansion. The Ti-Pd braze alloy enables successful hermetic sealing while simplifying the manufacturing process compared to direct ceramic-metal bonding.
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 Ti-Pd brazed interface provides a robust and bio-compatible seal, enhancing the magnetic inductance for RF power/data transmission and maintaining the integrity of the microstimulator's electronic components.
Implementation Method 1
heated to create a eutectic bond
Implementation Method 2
Ti-Pd brazed interface
Implementation Method 3
the Ti—Pd interlayer melts
Implementation Method 4
wets the ceramic surface and forms a bond with the ceramic
Data Source
AI summary
A component assembly for use in living tissue comprises: a ceramic part; a metal part; and a titanium palladium (Ti—Pd) interface layer for bonding said ceramic part to the metal part. In one embodiment, the interface layer may be formed from a single titanium layer in contact with a single palladium layer, or in other embodiments, may be at least a three layer laminate (Pd—Ti—Pd). A microstimulator housing comprising a ceramic part, a titanium or titanium alloy part sandwiching the Ti—Pd interlayer may be employed to create a eutectic bond that is strong and hermetic.