Laser Etched Ceramic Feedthrough for Hermetic Medical Seals
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Solution Overview
Problem
Designing hermetically protected circuit assemblies for implantable medical devices to operate effectively in a body tissue environment is challenging, particularly in maintaining a hermetic seal while allowing electrical signals to pass through, as moisture can cause failures and damage to feedthrough connections.
Innovation Solution
The use of a ceramic substrate with a laser-etched non-hermetic surface and metal pins or conductors that pass through it, coupled with a gold braze and encapsulated in epoxy, forms a robust feedthrough assembly that maintains the hermetic seal and enhances adhesion and moisture resistance, preventing mechanical failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hermetic seal is used to protect the metal case, then reliability is improved, but electrical signals cannot pass through the seal
Solution Approach 1:
The feedthrough structure segments the hermetic seal into distinct functional zones: a hermetic barrier portion that maintains the seal, and a non-hermetic signal transmission portion that allows electrical signals to pass. This segmentation enables both hermetic protection and electrical signal transmission simultaneously.
Solution Approach 2:
The feedthrough acts as an intermediary element that bridges the hermetic barrier and the electrical signal transmission requirements. It provides a controlled pathway for signals to pass through the hermetic seal while maintaining the integrity of the seal itself.
2Ease of operation
If I/O conductors pass through the hermetic seal, then electrical signal transmission is enabled, but moisture ingress occurs causing failures
Solution Approach 1:
The feedthrough exhibits different hermetic properties at different locations: the barrier portion maintains hermetic sealing to prevent moisture ingress, while the signal transmission portion is intentionally non-hermetic to allow electrical signals to pass. This local differentiation of quality enables both functions.
Solution Approach 2:
The feedthrough transitions from a two-dimensional planar seal to a three-dimensional structure with varying hermetic properties along its length. The hermetic barrier portion and non-hermetic signal transmission portion are arranged along the longitudinal dimension, enabling simultaneous hermetic protection and signal transmission.
3Ease of manufacture
If a smooth ceramic surface is used, then manufacturing is easier, but adhesion and moisture resistance are reduced
Solution Approach 1:
The surface roughness parameter of the ceramic feedthrough is intentionally modified to enhance adhesion properties. The laser-etched rough surface provides increased surface area and mechanical interlocking, improving adhesion of epoxy and resistance to moisture, while the smooth inner surface maintains manufacturing simplicity.
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 solution effectively prevents moisture ingress and maintains the hermetic seal, reducing mechanical failures and ensuring reliable operation of implantable medical devices by providing better adhesion and capillary action, thus ensuring the integrity of feedthrough connections.
Implementation Method 1
The non-hermetic surface of the ceramic substrate is a laser etched surface... providing better adhesion and capillary action, thus ensuring the integrity of feedthrough connections
Implementation Method 2
the ceramic substrate is coupled to the flange using a gold braze on an edge of the ceramic substrate
Implementation Method 3
The one or more I/O conductors and the laser etched surface of the ceramic substrate covered with an epoxy
Data Source
AI summary
A medical device comprises a metal case having a hermetic seal; one or more Input/Output (I/O) conductors, wherein the I/O conductors pass through the hermetic seal such that a first end of the I/O conductors reside on a non-hermetic side of the hermetic seal and a second end of the I/O conductors reside on a hermetic side of the hermetic seal within the metal case; a ceramic substrate, wherein the one or more I/O conductors pass through the ceramic substrate and the ceramic substrate has a non-hermetic surface on a non-hermetic side of the hermetic seal; and wherein the non-hermetic surface of the ceramic substrate is a laser etched surface.