Low-Temperature Gold Alloy Brazing for Titanium Implant Feedthroughs
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Solution Overview
Problem
Conventional methods for attaching feedthroughs to titanium housings in implantable medical devices face challenges such as grain growth, dimensional distortions, and weak joints due to high-temperature brazing or welding, which can lead to premature device failure and increased costs.
Innovation Solution
A low-temperature brazing process using a biocompatible gold alloy with a melting point below the β-transus temperature of titanium is employed to directly attach the feedthrough to the housing, eliminating the need for a ferrule and reducing grain growth, thereby forming a stronger and more consistent hermetic seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-temperature brazing or welding is used to attach feedthrough to housing, then strong joint is achieved, but grain growth occurs in titanium housing causing dimensional distortions and reduced rigidity
Solution Approach 1:
The patent changes the temperature parameter of the brazing process by selecting a braze material with a melting point specifically below the β-transus temperature of titanium (995°C). This parameter change prevents the thermal conditions that cause grain growth while maintaining sufficient heat to create a strong braze joint between the ferrule and housing.
Solution Approach 2:
The patent introduces a ferrule as an intermediary component made of a material compatible with low-temperature brazing. The ferrule serves as a mediator that can be firmly attached to the housing through controlled low-temperature brazing, thereby protecting the titanium housing from direct exposure to temperatures that would cause grain growth and dimensional distortions.
2Strength
If high-temperature brazing or welding is used to attach feedthrough to housing, then strong joint is achieved, but titanium rigidity about the opening is reduced
Solution Approach 1:
The patent changes the temperature parameter of the brazing process by selecting a braze material with a melting point specifically below the β-transus temperature of titanium (995°C). This parameter change prevents the thermal conditions that cause grain growth while maintaining sufficient heat to create a strong braze joint between the ferrule and housing.
3Reliability
If ferrule is machined to provide tight tolerance gap for braze joint, then quality braze joint is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the gap dimension parameter by specifying a larger gap range (0.05-0.50 mm) compared to conventional tight-tolerance braze joints. This relaxed gap specification dramatically reduces the machining precision requirements for the ferrule while still ensuring reliable braze joint formation, thereby reducing manufacturing complexity and cost.
4Ease of manufacture
If conventional brazing process is used, then feedthrough is attached to housing, but risk of weak joint and premature device failure increases
Solution Approach 1:
The patent changes the temperature parameter by selecting a braze material with a melting point below the β-transus temperature of titanium, preventing grain growth that would weaken the joint. This parameter change maintains the simplicity of the brazing process while significantly improving joint reliability and preventing premature device failure.
Solution Approach 2:
The patent introduces a ferrule as an intermediary component made of a material compatible with low-temperature brazing. The ferrule serves as a mediator that can be firmly attached to the housing through controlled low-temperature brazing, thereby protecting the titanium housing from direct exposure to temperatures that would cause grain growth and dimensional distortions.
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 approach results in a stronger, more reliable joint with reduced grain growth and dimensional distortions, maintaining the titanium's rigidity and ensuring the feedthrough is completely devoid of high-temperature welds or brazes, thus enhancing the durability and performance of the implantable medical device.
Implementation Method 1
A biocompatible braze material having a melting point less than a β-transus temperature of the titanium of the housing is melted to fill at least the gap
Implementation Method 2
the braze material is melted at a temperature less than the β-transus temperature of the titanium of the housing
Data Source
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AI summary
One aspect provides a method of attaching a feedthrough to a titanium housing of an implantable medical device. The method includes providing the housing with a flange forming a recess about an opening through the housing, the opening disposed within the recess. A feedthrough is positioned within the recess so as to form a gap between the flange and an insulator of the feedthrough. A braze preform is then positioned within the recess about the insulator, the braze preform comprising a biocompatible braze material having a melting point less than a β-transus temperature of the titanium of the housing. The preform is melted at a temperature less than the β-transus temperature of the titanium of the housing such that the melted braze material fills at least the gap, and then cooled to form a braze joint which bonds the insulator to the housing and hermetically seals the opening.