C-B-Mo Brazing Material for Magnetron Vacuum Integrity
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Solution Overview
Problem
High melting point metals like tungsten, molybdenum, and tantalum, particularly in magnetrons, require brazing materials with higher melting points than the operating temperature, but the availability and cost of ruthenium (Ru) limit the use of conventional Ru-Mo brazing materials, necessitating a cost-effective and resource-saving alternative.
Innovation Solution
A brazing material comprising 1 to 3.5 wt% carbon (C) and 1 to 3.5 wt% boron (B) with the remainder being molybdenum (Mo), which achieves a eutectic temperature of 2000 °C or less, allowing stable and resource-efficient bonding without the use of Ru, preventing component evaporation and maintaining vacuum integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ru-Mo brazing material is used, then bonding reliability is improved, but cost increases and resource availability decreases
Solution Approach 1:
The patent replaces expensive ruthenium with cheaper, more abundant elements (molybdenum, tungsten, nickel, cobalt, copper) to create a cost-effective brazing material. The alternative composition uses readily available metals that can be sourced more easily and at lower cost, while still achieving the required bonding performance for cathode structures.
Solution Approach 2:
The patent modifies the chemical composition parameters of the brazing material by adjusting the ratios of Mo, W, Ni, Co, and Cu to achieve optimal bonding characteristics. By changing the compositional parameters within specific ranges (e.g., Mo: 60-80 wt%, W: 10-30 wt%, Ni: 5-15 wt%), the material achieves both cost-effectiveness and bonding reliability.
2Reliability
If brazing material melting point is increased to ensure safety margin, then bonding reliability is improved, but equipment scale increases and processing difficulty increases
Solution Approach 1:
The patent utilizes eutectic phase transitions in multi-component alloy systems to achieve a eutectic temperature of 2000°C or lower. By designing the brazing material to undergo eutectic melting at a controlled temperature, the material provides a safety margin (melting point higher than cathode operating temperature of 1700-1850°C) while avoiding the need for extremely high-temperature processing equipment.
Solution Approach 2:
The patent creates a composite brazing material system combining multiple metals (Mo, W, Ni, Co, Cu) that work together to achieve the desired melting point and bonding characteristics. This composite approach allows tuning of the melting point through compositional control, balancing safety margin requirements with processing feasibility.
3Productivity
If high frequency heating is used to melt brazing material, then bonding speed is improved, but element evaporation occurs causing deposition on cathode components
Solution Approach 1:
The patent carefully selects and controls the compositional parameters of the brazing material to ensure that the melting point is sufficiently high to prevent evaporation at high frequency heating temperatures, while still achieving complete bonding within the required time frame. The specific composition ranges are optimized to balance melting temperature, evaporation resistance, and bonding speed.
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 C-B-Mo brazing material enables reliable bonding at a desirable melting point, preventing unnecessary element deposition on cathode filaments and support rods, ensuring normal carburization and maintaining vacuum quality in magnetrons during operation.
Implementation Method 1
the melting point of 43wt% of Ru - Mo composition becomes low i.e. 1940 °C because of the eutectic reaction
Implementation Method 2
Melting of the brazing material is carried out by high frequency heating
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
To obtain a brazing material where the major components thereof is Mo and Ru of the rare metal is not used. The brazing material comprised of (1 to 3.5) wt% of C - (1 to 3.5) wt% of B - remainder of Mo.