Titanium Oxide Electrode for Ceramic Pressure Cell Soldering
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Solution Overview
Problem
Existing pressure-measuring cells face challenges with temperature-dependent mechanical stresses due to the narrow temperature range for forming a high-quality pressure-tight connection using active brazing solder and the introduction of additional layers with different thermal coefficients of expansion, which affects the reliability and accuracy of pressure measurements.
Innovation Solution
A capacitive pressure-measuring cell with a ceramic measuring membrane and counter body joined using a zirconium-nickel-titanium active brazing solder, where the membrane electrode comprises titanium oxide, acting as both an electrode and a solder stop to prevent solder entry into the pressure chamber, and is prepared using techniques like sputtering and thermal oxidation to ensure a stable and conductive interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active brazing solder is used to join measuring membrane and counter body, then pressure-tight connection is achieved, but temperature range for soldering is narrowly limited
Solution Approach 1:
The patent changes the material parameter of the electrode from traditional metals (tantalum, niobium, silicon carbide) to titanium oxide. This material substitution modifies the thermal and chemical properties of the electrode-solder interface, enabling the solder to maintain appropriate viscosity and reactivity over a broader temperature range while still achieving reliable pressure-tight connections.
Solution Approach 2:
Titanium oxide serves as an intermediary material between the active brazing solder and the ceramic measuring membrane. This intermediate layer facilitates controlled interaction between the solder and ceramic surfaces, improving wetting behavior and connection reliability across a wider temperature window by mediating the thermal and chemical processes at the interface.
2Reliability
If oxidation of tantalum electrode surface is used as solder stop, then solder entry into pressure chamber is prevented, but temperature hysteresis is caused due to different thermal coefficients of expansion
Solution Approach 1:
The titanium oxide electrode performs multiple functions simultaneously: it serves as the capacitive transducer electrode for pressure detection and also acts as a solder stop to prevent solder intrusion into the pressure chamber. This eliminates the need for separate tantalum electrode and oxidation layer, thereby avoiding the thermal expansion mismatch that causes measurement hysteresis.
Solution Approach 2:
The patent extracts and eliminates the problematic two-layer electrode structure (metallic tantalum plus tantalum oxide) and replaces it with a single titanium oxide electrode. This removal of the layered structure eliminates the source of differential thermal expansion and the associated measurement errors while retaining the solder stop function.
3Manufacturing precision
If soldering temperature is increased to improve solder flow, then solder spreads better on surface, but solder enters areas not meant to be wetted
Solution Approach 1:
Changing the electrode material to titanium oxide modifies the thermal and surface properties of the electrode, allowing for controlled solder wetting at elevated temperatures. The titanium oxide surface provides appropriate wettability characteristics that enable uniform solder distribution without uncontrolled flow into restricted areas, thus maintaining pressure chamber integrity.
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 expands the temperature range for reliable soldering, reduces mechanical stresses by matching thermal expansion coefficients, and enhances conductivity, resulting in improved pressure measurement accuracy and reliability.
Implementation Method 1
reduces mechanical stresses by matching thermal expansion coefficients
Implementation Method 2
prepared using techniques like sputtering and thermal oxidation
Implementation Method 3
prepared using techniques like sputtering and thermal oxidation
Implementation Method 4
a capacitive transducer for converting the pressure-dependent deformation of the measuring membrane into an electrical signal
Data Source
AI summary
A pressure-measuring cell having a ceramic measuring membrane and a ceramic counter body, wherein the measuring membrane is joined to the counter body in such a way that a pressure chamber is formed between the measuring membrane and the counter body. The pressure-measuring cell also has a capacitive transducer for detecting a pressure-dependent deformation of the measuring membrane, which capacitive transducer has at least one membrane electrode arranged on the measuring membrane and at least one electrode on the counter body side, wherein according to the invention at least one membrane electrode comprises a titanium oxide.