Hermetic Ceramic Feedthrough via Segmented Lamination
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Solution Overview
Problem
Existing methods for forming hermetic electrical feedthroughs in ceramic sheets are limited in miniaturization, as they require a minimum diameter of >1mm and are not suitable for thin ceramic substrates ≤ 1 mm, which is a challenge for biocompatible and electrochemically stable medical devices implanted in the body.
Innovation Solution
A method involving the formation of via holes in ceramic sheets, filling them with conductive thickfilm paste, stacking and laminating the sheets, and firing to create metalized vias with a hermetic seal, allowing for high feedthrough density and miniaturization down to ≤ 0.5 mm diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional tube cofiring method is used, then hermetic seal is achieved, but feedthrough diameter is limited to >1mm
Solution Approach 1:
The ceramic substrate is divided into multiple thin layers (first ceramic layer, second ceramic layer, third ceramic layer) that are stacked and cofired together. The via holes are formed through these segmented layers, allowing each layer to be optimized independently and enabling smaller feedthrough dimensions than possible with a single thick ceramic piece.
Solution Approach 2:
The invention transitions from a single-plane via hole approach to a three-dimensional stacked layer structure. Multiple ceramic layers are arranged vertically with via holes extending through each layer, creating a multi-dimensional configuration that reduces the minimum feasible feedthrough diameter while maintaining hermetic sealing.
2Volume of moving object
If ceramic sheet thickness is reduced to ≤1mm, then device miniaturization is achieved, but hermetic seal reliability deteriorates
Solution Approach 1:
Instead of using a single thin ceramic sheet, the invention segments the ceramic structure into multiple thinner layers stacked together. This segmentation allows the via holes to pass through multiple interfaces, creating redundant sealing paths and distributing stress, thereby maintaining hermetic reliability even when the overall thickness is reduced to ≤1mm.
Solution Approach 2:
The invention creates a composite ceramic structure by cofiring multiple ceramic layers with conductive material filled via holes. The combination of multiple ceramic layers bonded together forms a composite material system that provides enhanced mechanical strength and hermetic sealing capability compared to a single thin ceramic sheet.
3Reliability
If via holes are filled with conductive paste and cofired, then electrical conductivity is achieved, but manufacturing complexity increases
Solution Approach 1:
The invention merges multiple fabrication operations into a single cofiring step. The ceramic layers, via hole formations, conductive paste filling, and sealing operations are combined into one integrated cofiring process, reducing the total number of separate manufacturing steps while achieving electrical conductivity and hermetic sealing simultaneously.
Solution Approach 2:
The via holes are formed and conductive paste is applied to the ceramic layers before the final cofiring process. This preliminary preparation allows the conductive material to be positioned accurately within the via holes prior to firing, ensuring proper electrical connectivity while simplifying the overall manufacturing sequence.
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 enables the creation of hermetic, biocompatible, and electrochemically stable electrical feedthroughs with high density and miniaturization, suitable for medical devices, achieving a hermetic seal in thin ceramic substrates ≤ 1 mm thick, enhancing compatibility and stability in corrosive environments.
Implementation Method 1
firing the laminated ceramic substrate to a temperature to sinter the laminated ceramic substrate and cause the paste filled via holes to form metalized vias
Implementation Method 2
The hermeticity of the metal/ceramic interface is achieved by a compression seal formed by material shrinkage when the assembly is fired and then allowed to cool
Data Source
Figure 1~2
Figure 3
Figure 4A~4E
AI summary
A method for fabricating the hermetic electrical feedthrough. The method comprises providing a ceramic sheet having an upper surface and a lower surface, forming at least one via hole in said ceramic sheet extending from said upper surface to said lower surface, inserting a conductive thickfilm paste into said via hole, laminating the ceramic sheet with paste filled via hole between an upper ceramic sheet and a lower ceramic sheet to form a laminated ceramic substrate, firing the laminated ceramic substrate to a temperature to sinter the laminated ceramic substrate and cause the paste filled via hole to form metalized via and cause the laminated ceramic substrate to form a hermetic seal around said metalized via, and removing the upper ceramic sheet and the lower ceramic sheet material from the fired laminated ceramic substrate to expose an upper and a lower surface of the metalized via.