X-ray Tube Anode Bonding with Composite Heat Spreader
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Solution Overview
Problem
Conventional X-ray tube heat spreader materials like copper and silver suffer from thermal expansion mismatches with the anode, leading to high stresses, and existing methods fail to securely attach the anode to the heat spreader in harsh X-ray tube environments with high temperatures, temperature gradients, and high radiation.
Innovation Solution
A composite heat spreader made of molybdenum and copper, with a gold bonding layer, is used to securely attach the anode, employing diffusion bonding or brazing to create a reliable joint that withstands extreme conditions, and a corrosion-resistant gold layer is applied to prevent heat spreader corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If copper or silver heat spreader materials are used, then high thermal conductivity is achieved, but thermal expansion mismatch with the anode causes high stresses
Solution Approach 1:
The patent applies composite materials by creating a heat spreader composed of multiple layers: a copper base layer providing high thermal conductivity, and an intermediate layer (such as molybdenum or tungsten) with thermal expansion properties matched to the anode material. This composite structure combines the advantages of different materials - the copper ensures efficient heat dissipation while the intermediate layer accommodates thermal expansion differences, thereby resolving the contradiction between high thermal conductivity and thermal expansion stress.
2Reliability
If the anode is securely attached to the heat spreader, then reliable heat transfer is achieved, but existing attachment methods fail in harsh X-ray tube environments
Solution Approach 1:
The patent employs an intermediate layer as a mediator between the anode and the copper heat spreader. This intermediate layer (such as molybdenum or tungsten) serves multiple functions: it provides a thermal expansion match to the anode, creates a stable bonding surface, and protects both the anode and copper from the harsh X-ray tube environment including high temperatures, temperature gradients, and radiation. This intermediary structure enables reliable attachment while withstanding environmental challenges.
Solution Approach 2:
The multi-layer composite heat spreader structure creates a gradient of material properties from the anode interface to the copper base. Each layer is selected for specific properties that address environmental challenges, creating a composite structure that collectively provides both secure attachment and harsh environment resistance.
3Power
If high power operation is enabled, then X-ray tube performance is improved, but anode temperature increases causing evaporation or melting
Solution Approach 1:
The intermediate layer acts as a thermal mediator that facilitates efficient heat transfer from the anode to the copper heat spreader. This layered structure optimizes the thermal pathway, enabling the system to handle higher power loads by effectively conducting heat away from the anode, thereby preventing temperature-related failures during high power operation.
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 an X-ray tube anode arrangement with improved heat sinking properties, reduced plastic deformation, and extended tube life, capable of withstanding high temperatures, radiation, and rapid power switches, maintaining high vacuum properties and secure anode attachment.
Implementation Method 1
employing diffusion bonding or brazing to create a reliable joint
Implementation Method 2
brazing the anode to the heat spreader, i.e. softening the joint material by greater heat than used for diffusion bonding
Implementation Method 3
heat spreader materials with a high thermal conductivity are necessary to keep the anode temperature as low as possible
Implementation Method 4
such materials can have thermal expansion mismatches with the anode material which can lead to high stresses
Data Source
Figure 1
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AI summary
A method of manufacturing an X-ray tube component, includes diffusion bonding or brazing an anode (2) of rhodium, molybdenum or tungsten to a heat spreader (4) of molybdenum, tungsten, or a composite of molybdenum and/or tungsten. Suitable joint materials (10) for diffusion bonding include gold; suitable joint materials for brazing include an alloy of silver and copper, an alloy of silver, copper and palladium, an alloy of gold and copper or an alloy of gold, copper and nickel. The resulting tube component delivers reliable behaviours and the joint can withstand high temperatures, high temperature gradients, fast temperature changes, extremely high radiation and extremely high electric field, while maintaining good high vacuum properties.