Glass-Sheathed Ceramic Sensor Contacts for High-Temperature Reliability
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Solution Overview
Problem
Current temperature sensors face limitations in operating temperature, reliability, and manufacturing costs, particularly due to the use of noble metals and corrosion issues with FeNi wires, and existing solutions like solder joints and sintering pastes are not sufficient for high-temperature applications.
Innovation Solution
A high-temperature sensor arrangement using a ceramic base body with drift-stable perovskite ceramic and lead-free gold or silver thick-film metallization, combined with nickel-iron alloy or silver contacting elements and a recrystallizing barium zinc silicate glass sheath, which provides mechanical stability and corrosion resistance up to 650°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If solder joints are used for electrical contacting, then ease of manufacture is improved, but reliability deteriorates at high temperatures due to melting and migration
Solution Approach 1:
The patent changes the temperature parameter threshold by using sintering paste contacting instead of solder joints. The sintering paste can withstand temperatures above 250°C to 300°C, while solder joints melt below these temperatures. This parameter change in material selection based on temperature resistance resolves the contradiction between ease of manufacture and reliability at high temperatures.
Solution Approach 2:
The patent uses sintering paste as a consumable material that is applied and then fired to create permanent electrical contact. This replaces the reusable solder joint approach, accepting the higher initial process cost but achieving superior long-term reliability at high temperatures without the need for rework or replacement.
2Reliability
If sintering paste with gold metallization is used for high temperature contacting, then reliability is improved, but manufacturing cost deteriorates
Solution Approach 1:
The patent applies different metallization qualities to different functional areas: gold or silver paste is used specifically at the electrode contact points where electrical conductivity is critical, while the bulk of the sensor element uses less expensive materials. This local differentiation of material quality maintains reliability at the critical interface while reducing overall manufacturing cost.
Solution Approach 2:
The patent uses sintering paste with controlled noble metal content - not fully gold throughout, but sufficient gold or silver at the critical contacting areas to ensure reliability. This partial application of expensive material achieves the necessary reliability without the excessive cost of complete gold metallization throughout the entire sensor.
3Reliability
If glass encapsulation is used for high temperature protection, then reliability is improved, but manufacturing cost and process complexity deteriorate
Solution Approach 1:
The patent merges multiple functions into the glass encapsulation process: mechanical protection, environmental sealing, and electrical insulation are all achieved through the single glass encapsulation step. This consolidation of functions into one process step improves reliability while minimizing the addition of separate manufacturing steps and associated costs.
Solution Approach 2:
The patent uses glass as a composite encapsulation material that combines multiple desirable properties: high temperature resistance, chemical inertness, mechanical strength, and electrical insulation. This single composite material solution provides all necessary protection functions simultaneously, improving reliability without requiring multiple separate components or processes.
4Ease of manufacture
If FeNi wires with copper sheath are used for contacting, then manufacturing cost is improved, but reliability deteriorates due to wire corrosion at high temperatures
Solution Approach 1:
The patent replaces the FeNi wire with copper sheath with sintering paste and noble metal electrodes. The sintering paste acts as a consumable material that is fired to create a permanent, corrosion-resistant electrical connection. This eliminates the copper sheath that would corrode at high temperatures, achieving superior reliability while maintaining cost-effectiveness through the use of sintering technology.
Solution Approach 2:
The patent introduces sintering paste as an intermediary material between the electrode and the contacting element. This sintering paste, when fired, creates a metallurgical bond that is resistant to high temperature corrosion, serving as a protective intermediary that prevents direct exposure of the electrode to corrosive environments while maintaining electrical conductivity.
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 enables a cost-effective, durable, and corrosion-resistant sensor arrangement that maintains mechanical strength and electrical conductivity at high temperatures, overcoming the limitations of existing technologies.
Implementation Method 1
The electrodes have a gold or silver thick-film metallization
Implementation Method 2
The sensor arrangement has a glass sheath which is applied over the sensor element and the connection region
Implementation Method 3
the sensor element comprises an NTC thermistor chip
Data Source
AI summary
In an embodiment a sensor arrangement includes a sensor element including a ceramic base body and at least two electrodes, wherein the electrodes are arranged on an outer side of the ceramic base body, at least two contacting elements configured for making electrical contact with the sensor element, the contacting elements being connected to the electrodes in a connection region and a glass sheath, wherein at least the ceramic base body and the connection region are completely enclosed in the glass sheath, wherein the glass sheath is pressure tensioned, and wherein a coefficients of expansion of the glass sheath, the contacting elements and the sensor element are adapted to one another for the pressure tensioning of the glass sheath.