Pt-Ni Hermetic Feedthrough Seals for CTE Stress Control
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Solution Overview
Problem
Existing hermetic electrical feedthroughs face challenges in achieving a proper coefficient of thermal expansion (CTE) match between metal pins and glass-ceramic seals, leading to residual tensile stresses and potential cracking, especially under thermal shock conditions.
Innovation Solution
A hermetic electrical feedthrough system using a platinum-nickel-based pin alloy, such as Deriney-72, sealed with a belt processable S (BPS) glass-ceramic, where a specific thermal sealing profile is developed to achieve a CTE compatibility with the stainless steel shell and pin, maintaining compressive stresses and preventing cracking across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a palladium-silver pin alloy is used in previous high performance electrical feedthroughs, then hermetic sealing can be achieved, but a complex heat treatment process is required to age-harden the alloy and achieve proper CTE match
Solution Approach 1:
The invention changes the material composition parameters by using a Pt-Ni-based alloy with specific ternary or higher additions (such as Pt-Ni-Re, Pt-Ni-Ir, Pt-Ni-Pd) instead of traditional Pd-Ag alloys. This compositional parameter change enables the alloy to achieve both hermetic sealing capability and CTE matching with glass-ceramic without requiring complex age-hardening heat treatment processes, thus resolving the contradiction between reliability and process complexity
Solution Approach 2:
The invention employs composite material design by creating a Pt-Ni-based alloy system with multiple elemental additions (ternary or higher). This composite alloy structure provides synergistic effects where the base Pt-Ni alloy offers hermetic sealing properties while the additional elements (Re, Ir, Pd, etc.) contribute to CTE adjustment and microstructure control, eliminating the need for complex heat treatment while maintaining sealing reliability
2Stress or pressure
If the CTE of glass-ceramic is altered to match the shell or pin, then residual tensile stresses are minimized, but maintaining compressive stresses along interfaces that maintain hermeticity becomes challenging
Solution Approach 1:
The invention changes the CTE parameter of the glass-ceramic through controlled crystallization processes and compositional adjustments, achieving a CTE value that simultaneously minimizes residual tensile stresses and maintains compressive stresses at the hermetic interfaces. The Pt-Ni-based pin alloy also contributes to this solution by providing a CTE that is compatible with the optimized glass-ceramic, creating a balanced stress state that preserves hermeticity
Solution Approach 2:
The invention applies local quality by creating different stress states in different regions of the glass-ceramic assembly. The bulk glass-ceramic is designed to have minimal tensile stresses through CTE matching, while the interfaces with the shell and pin are engineered to maintain compressive stresses through controlled thermal processing and material selection, thereby preserving hermeticity at critical locations without compromising overall stress distribution
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 system ensures a hermetic seal with reduced residual stresses, higher hardness, and improved robustness against thermal shock, maintaining hermeticity even after extreme temperature treatments, and preventing interdiffusion and phase formation issues.
Implementation Method 1
A thermal sealing profile was developed to generate a CTE in the glass-ceramic which is compatible with the Deriney-72 pin material
Implementation Method 2
maintains a compressive stress state within the glass-ceramic throughout most of the temperature range from −55 to +500° C.
Implementation Method 3
exhibits less interdiffusion and phase formation and, therefore, a uniform microstructure in the bulk and near the pin/glass-ceramic interface
Data Source
AI summary
A combination of materials and processing parameters have been developed for hermetic seals for electrical feedthroughs in high performance applications. A glass-ceramic forms a hermetic seal between a stainless steel shell and a platinum-nickel-based (Pt—Ni) pin alloy for electrical feedthroughs. The glass-ceramic is processed to develop a coefficient of thermal expansion (CTE) slightly higher than the pin alloy but lower than the stainless steel. The seal system employing the new processing conditions and Pt—Ni-based pin alloy alleviates several problems encountered in previous seal systems and improves the hermetic connector performance.