Ferrule Flange Geometry for Non-Planar Housing Weld Sealing
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Solution Overview
Problem
Non-planarity of the housing surface in implantable medical devices can lead to weld failures between the ferrule and housing, resulting in an incomplete hermetic seal, which is a challenge in achieving a reliable electrical connection for implantable medical devices.
Innovation Solution
A ferrule design with a frame body that includes a housing flange and insulator flange, allowing for a butt-weld instead of a lap-weld, which tolerates greater non-planarity by maintaining specific thickness and positional relationships between the ferrule and housing, ensuring a successful weld even with non-planar surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a lap-weld is used to attach the ferrule to the housing, then the welding process is simpler, but the tolerance for non-planarity in the housing surface is insufficient leading to weld failure
Solution Approach 1:
The patent transitions from a lap-weld configuration to a butt-weld configuration by changing the dimensional relationship between the ferrule and housing. The ferrule is positioned such that its welding surface is coplanar with the housing outer surface, creating a butt-joint geometry that tolerates non-planarity better than the overlapping lap-weld geometry.
Solution Approach 2:
The patent changes the critical geometric parameters of the ferrule, specifically the thickness and positional relationship of the welding surfaces. By adjusting these parameters to create a butt-weld configuration, the system achieves increased tolerance for housing surface non-planarity while maintaining weld integrity.
2Device complexity
If the ferrule thickness and position are not precisely controlled, then manufacturing is more flexible, but weld reliability decreases due to non-planarity
Solution Approach 1:
The patent establishes predetermined relationships between the ferrule thickness and its positional offset from the housing outer surface. These preliminary dimensional specifications ensure that when the ferrule is welded to the housing, the welding surfaces are coplanar, thereby ensuring weld reliability without requiring complex real-time adjustments during manufacturing.
3Manufacturing precision
If a butt-weld configuration is implemented with coplanar surfaces, then tolerance for non-planarity increases, but the ferrule design becomes more complex
Solution Approach 1:
The patent applies local quality by creating a specific coplanar interface zone on the ferrule where the welding occurs. While the overall ferrule design remains relatively simple, the local region at the welding surface is precisely engineered to be coplanar with the housing outer surface, providing the necessary tolerance for non-planarity without complicating the entire device.
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 ferrule design significantly increases the tolerance for non-planarity in the housing surface, enabling successful welds with up to twice the previous tolerance, thus ensuring a reliable hermetic seal and reducing the risk of weld failure, while minimizing the impact on the braze connection.
Implementation Method 1
The ferrule, in-turn, is arranged to fit within a corresponding opening in the metal housing and is attached thereto, typically via welding (e.g., laser welding), to form a hermetic seal
Implementation Method 2
the insulator serves to electrically insulate the feedthrough pins from one another and from the metal ferrule and housing
Implementation Method 3
the ferrule and insulator being joined to one another, such as by a brazing or soldering process, for example
Implementation Method 4
the ferrule and insulator being joined to one another, such as by a brazing or soldering process, for example
Data Source
AI summary
One example provides a ferrule for an implantable medical device including a frame body having an upper surface and an opposing lower surface, an interior perimeter surface extending between the upper and lower surfaces for attachment to an insulator body, and an exterior perimeter surface extending between the upper and lower surfaces for attachment to a housing. A flange extends from the exterior perimeter surface and has an upper surface facing the upper surface of the frame body, the upper surface of the flange to engage an interior surface of a housing of the implantable medical device to limit a position of the housing along the exterior perimeter surface in a direction toward the bottom surface of the frame body, wherein a distance of the top surface of the flange from the top surface of the frame body is greater than and proportional to a thickness of the housing.