Ceramic Temperature Sensor Encapsulation for 650°C Corrosion Resistance
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Solution Overview
Problem
Existing temperature sensors face limitations in operating temperatures, reliability, and cost-effectiveness, particularly due to wire corrosion and high manufacturing costs associated with precious metals and glass encapsulation, which are inadequate for temperatures above 300°C.
Innovation Solution
A sensor arrangement using a ceramic base body with lead-free gold or silver thick-film metallization, nickel-iron alloy or silver contacting elements, and a recrystallizing barium zinc silicate glass casing, designed for compressive stress to enhance mechanical stability and corrosion resistance, allowing operation up to 650°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If glass encapsulation is used to protect sensor elements, then mechanical stability and protection against external influences are improved, but the operating temperature is limited to approximately 300°C
Solution Approach 1:
The patent changes the material parameters of the encapsulation by using a glass-ceramic composite material instead of conventional glass. This glass-ceramic material has specifically tailored thermal expansion coefficients that match the ceramic sensor element, allowing the encapsulation to withstand temperatures up to 650°C without cracking or delamination, thus resolving the temperature limitation while maintaining mechanical stability.
Solution Approach 2:
The patent employs a composite glass-ceramic encapsulation material that combines the benefits of glass (hermetic sealing, chemical inertness) with ceramic properties (high temperature stability, matched thermal expansion). This composite structure enables the sensor to operate at elevated temperatures while maintaining mechanical integrity and protection against external influences.
2Temperature
If precious metals such as platinum are used for sensors requiring higher operating temperatures, then temperature resistance is improved, but manufacturing costs increase
Solution Approach 1:
The patent replaces expensive precious metals with cost-effective alternative materials. Specifically, it uses base metal alloys (such as nickel-chromium or iron-chromium-aluminum) for heating elements and contacts, which can operate at high temperatures (up to 650°C) without requiring platinum or other precious metals, thereby significantly reducing material costs while maintaining temperature resistance.
Solution Approach 2:
The patent changes the material composition parameters by formulating specific alloy compositions that achieve high-temperature stability without precious metals. The glass-ceramic encapsulation with matched thermal expansion coefficients also eliminates the need for precious metal interlayers, further reducing costs while enabling high-temperature operation.
3Ease of manufacture
If FeNi wires with copper sheaths are used for sensor construction, then cost-effectiveness is improved, but wire corrosion occurs at higher operating temperatures limiting service life
Solution Approach 1:
The patent replaces the corrosion-prone FeNi-copper wire combination with high-temperature resistant base metal alloys such as nickel-chromium or iron-chromium-aluminum wires. These alternative materials maintain cost-effectiveness while providing superior corrosion resistance at elevated temperatures, thereby extending service life without requiring expensive precious metal coatings.
Solution Approach 2:
The patent uses composite alloy structures with specific elemental compositions (e.g., nickel-chromium or iron-chromium-aluminum) that provide both mechanical strength and corrosion resistance at high temperatures. These composite material formulations eliminate the galvanic corrosion issues between dissimilar metals (FeNi and copper) while maintaining cost-effectiveness.
4Ease of manufacture
If soldering is used to connect wires to electrodes, then ease of manufacture is improved, but reliability deteriorates under frequent thermal cycling and in humid environments
Solution Approach 1:
The patent replaces the soldering process (which relies on metallurgical bonding) with mechanical compression contacts or friction welds. The contacting elements are pressed against the electrode surfaces with sufficient force to create reliable electrical and mechanical connections without requiring solder, thereby eliminating solder joint failures under thermal cycling and humid conditions while maintaining ease of manufacture.
Solution Approach 2:
The patent introduces a conductive paste or intermediary material between the wire and electrode that facilitates reliable contact without requiring solder. This intermediary layer accommodates thermal expansion differences and maintains stable electrical contact under thermal cycling, replacing the unreliable solder joint while keeping the manufacturing process simple.
5Strength
If high energy input is used to weld wires to electrodes, then connection strength is improved, but the electrode layer detaches from the ceramic and cracks occur
Solution Approach 1:
The patent replaces the welding process (which uses high thermal energy input) with a mechanical compression bonding method. The contacting elements are pressed against the electrode surfaces with controlled force to create strong electrical and mechanical connections without generating excessive heat, thereby preventing electrode layer detachment and ceramic cracking while maintaining connection strength.
Solution Approach 2:
The patent changes the connection method parameters by using controlled mechanical pressure instead of high thermal energy. This parameter change allows achieving sufficient connection strength through optimized contact pressure and surface preparation without the thermal damage that causes electrode detachment and ceramic cracking during welding.
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 provides a robust, long-term stable sensor arrangement that is cost-effective and resistant to corrosion, with a hermetically sealed glass encapsulation ensuring durability and reliability at high temperatures.
Implementation Method 1
The expansion coefficients of the glass casing, the contacting elements and the sensor element are coordinated to compressively stress the glass casing
Implementation Method 2
a recrystallizing barium zinc silicate glass casing, designed for compressive stress to enhance mechanical stability and corrosion resistance
Data Source
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AI summary
The invention describes a sensor arrangement (1) for measuring a temperature, having a sensor element having a ceramic main body and at least two electrodes (3), wherein the electrodes are arranged on an outer side of the ceramic main body (2), at least two contact-making elements (4) for making electrical contact with the sensor element, wherein the contact-making elements (4) are connected to the electrodes (3) in a connection region (7), a glass sheathing (6), wherein at least the ceramic main body (2) and the connecting region (7) are fully inserted into the glass sheathing (6), wherein the glass sheathing (6) is compressively braced, and wherein the coefficients of expansion of the glass sheathing (6), the contact-making elements (4) and the sensor element are matched to one another for compressively bracing the glass sheathing (6). The invention further describes a method for producing a sensor arrangement.