Thermal Head Electrode Oxygen Gradient for Adhesion
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Solution Overview
Problem
In thermal heads, the mismatch in thermal expansion coefficients between the electrode and the protective layer can lead to void formation and decreased adhesion between them.
Innovation Solution
Incorporating a first region below 150 nm from the surface of the electrode with oxygen content, and a second region extending up to 150 nm, which brings the thermal expansion coefficient of the electrode closer to that of the protective layer, reducing stress and void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrode is made with standard material composition, then electrical conductivity is maintained, but the coefficient of thermal expansion mismatch with the protective layer causes void formation and adhesion decrease
Solution Approach 1:
The patent changes the chemical composition parameters of the electrode by incorporating oxygen at specific concentrations (1-13 atomic percent in the first region, 1-50 atomic percent in the second region). This parameter change adjusts the coefficient of thermal expansion of the electrode to match that of the protective layer, resolving the thermal expansion mismatch issue while maintaining electrical conductivity
Solution Approach 2:
The patent applies local quality by creating regions with different oxygen concentrations within the electrode. The first region (deeper layer) has 1-13 atomic percent oxygen while the second region (surface layer within 150 nm) has 1-50 atomic percent oxygen. This gradient structure allows the electrode to have optimized thermal expansion properties at the interface with the protective layer while maintaining bulk electrical conductivity
2Reliability
If oxygen is added to the electrode to match thermal expansion coefficients, then adhesion improves, but electrode composition becomes more complex
Solution Approach 1:
Rather than adding a separate layer or complex composite structure, the patent simplifies the solution by changing the composition parameter (oxygen content) within the existing electrode material itself. This approach achieves the thermal expansion matching function through compositional adjustment rather than structural complexity
Solution Approach 2:
The patent creates a composite electrode structure by incorporating oxygen into the electrode material matrix. This forms an oxygen-containing electrode composite that exhibits modified thermal expansion properties while maintaining the fundamental electrode functionality, effectively using composite material principles to resolve the contradiction
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 enhances adhesion and reduces the likelihood of voids between the electrode and the protective layer, maintaining electrode function while improving thermal efficiency and corrosion resistance.
Implementation Method 1
the coefficient of thermal expansion of the electrode can be brought close to the coefficient of thermal expansion of the protective layer
Data Source
AI summary
To provide a thermal head in which separation of a protective layer is unlikely to occur. A thermal head X1 includes a substrate 7, a heat-generating portion 9 disposed on the substrate 7, electrodes 17 and 19 disposed on the substrate 7 and electrically connected to the heat-generating portion 9, and a protective layer 25 which covers the heat-generating portion 9 and part of the electrodes 17 and 19. The electrodes 17 and 19 each includes a first region R1 which lies below a depth of 150 nm from the surface 17e or 19e located on the protective layer 25 side, and the first region R1 contains oxygen. It is possible to suppress separation of each of the electrodes 17 and 19 from the protective layer 25.