Ceramic Heater Bonding via Metallic Layer and Brazing
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Solution Overview
Problem
Existing heater designs face challenges in achieving reliable bonding between ceramic and metallic components, leading to potential electrical leakage and reduced long-term reliability due to thermal stress and corrosion, especially when used in applications like electronic bidets where water is involved.
Innovation Solution
A heater design featuring a ceramic body with a heat generating resistor and a metallic flange bonded using a metallic layer and brazing material, with an additional metallic wire that has a higher thermal expansion coefficient than the ceramic, enhancing bonding strength and sealing while reducing thermal stress and corrosion risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ceramic body with heat generating resistor is directly bonded to a metallic flange using conventional bonding methods, then the structure is simple, but the bonding strength is insufficient and electrical leakage occurs due to poor sealing
Solution Approach 1:
The patent employs a composite bonding structure consisting of a metallic layer deposited on the ceramic body and a eutectic brazing material that forms an intermetallic compound layer. This composite approach combines the advantages of both metallic bonding (electrical conductivity) and ceramic bonding (thermal stability), achieving strong, sealed bonds that prevent electrical leakage while maintaining structural integrity under thermal stress.
Solution Approach 2:
The eutectic brazing material acts as an intermediary between the metallic layer on the ceramic body and the aluminum alloy flange. This intermediate layer facilitates controlled bonding by forming specific intermetallic compounds (Al-Cu-Fe phases) that create a gradient transition, reducing thermal stress concentration and improving bonding strength while maintaining electrical insulation where needed.
2Duration of action of stationary object
If conventional bonding materials are used between ceramic and metal components, then the manufacturing process is simple, but thermal stress causes bonding failure and corrosion over time
Solution Approach 1:
The patent utilizes the eutectic composition of the brazing material (4-14 wt% Cu, 2-6 wt% Fe, balance Al) which melts at a specific temperature range, enabling controlled bonding. The intermetallic compound layer formation is also a parameter-controlled process where the thickness (0.5-5 μm) and composition are optimized to balance bonding strength and thermal stress resistance, ensuring long-term durability.
Solution Approach 2:
The patent addresses thermal expansion mismatch between ceramic and metal components by creating a gradient intermetallic compound layer through controlled diffusion during brazing. This gradient structure gradually transitions from Al-rich phases at the flange interface to Cu-Fe-rich phases at the ceramic interface, distributing thermal stress more evenly and preventing bonding failure under thermal cycling.
3Strength
If a metallic layer and brazing material are used to bond ceramic and flange, then bonding strength improves, but manufacturing complexity increases
Solution Approach 1:
The patent merges the functions of the metallic layer and the brazing material into a unified bonding system. The metallic layer (formed by sputtering or plating) and the eutectic brazing material work synergistically during the brazing process, where the brazing material penetrates and bonds to the metallic layer, creating a consolidated bonding interface that achieves high strength without requiring separate complex bonding steps.
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 design improves bonding strength and sealing between the ceramic and metallic components, reducing the risk of electrical leakage and enhancing long-term reliability by distributing thermal stress and minimizing corrosion, thus ensuring effective heat transfer and durability.
Implementation Method 1
a heat generating resistor 2 disposed in an interior of the ceramic body 1
Implementation Method 2
the metallic layer 3 and the flange 7 are bonded with each other with a bonding material 6
Implementation Method 3
a metallic wire 8 that extends along a circumferential direction of the ceramic body 1 and has a higher thermal expansion coefficient than the ceramic body 1
Data Source
Figure 1
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AI summary
A heater includes a ceramic body having a pillar or cylindrical shape; a heat generating resistor disposed in an interior of the ceramic body; a metallic layer which is disposed on an outer peripheral surface of the ceramic body and extends along a circumferential direction thereof; a flange bonded to the metallic layer via a bonding material, the bonding material including a meniscus part extending from the metallic layer to the flange; and a metallic wire which is disposed in an interior of the meniscus part on the outer peripheral surface of the ceramic body and extends along the circumferential direction.