Liquid Discharging Head Substrate Thermal Stress Durability
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Solution Overview
Problem
The existing liquid-discharging-head substrates face challenges in densely arranging heating resistor elements while maintaining high durability and low power consumption, as the formation of thin heating resistor elements on recessed portions can lead to oxidation and reduced durability, and thickening the elements to improve step coverage increases resistance value and power consumption.
Innovation Solution
A liquid-discharging-head substrate design featuring an insulation layer with strategically formed openings and electrodes, where the insulation layer is flattened using CMP to create recessed portions, allowing for the formation of a heating resistor element layer with improved step coverage and durability, and the corner portions of the insulation layer are selectively etched to ensure the heating resistor element layer is formed on a smooth surface, preventing oxidation and maintaining low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heating resistor element layer is formed on the recessed portion created by CMP flattening, then the step coverage is improved and durability is enhanced, but the manufacturing process complexity increases due to additional CMP and etching steps
Solution Approach 1:
The insulation layer surface is preliminarily flattened using CMP processing before forming the heating resistor element layer. This preliminary flattening action creates a smooth base surface that prevents oxidation and ensures uniform thickness of the heating resistor element layer, thereby improving durability without requiring complex additional processing steps during the heating element formation stage
Solution Approach 2:
The corner portions of the insulation layer are selectively removed through etching to create recessed portions. This extraction of problematic corner regions eliminates areas where oxidation could occur and ensures that the heating resistor element layer is formed only on smooth, flat surfaces, thereby enhancing durability while maintaining manufacturing feasibility
2Use of energy by moving object
If the heating resistor element layer is made thin to reduce power consumption, then energy efficiency is improved, but oxidation occurs on recessed portions reducing durability
Solution Approach 1:
The CMP flattening process, which could potentially remove material and create variability, is utilized to create a uniformly smooth surface that eliminates recessed portions prone to oxidation. By converting the potential harm of material removal into the benefit of surface uniformity, thin heating resistor element layers can be formed without oxidation, achieving both low power consumption and high durability
Solution Approach 2:
The patent creates an inert environment by forming the heating resistor element layer on a smooth, flattened surface that is less susceptible to oxidation. The CMP-processed surface and selective etching of corner portions create a structure where the heating element is protected from oxidative environments, enabling thin layer formation that maintains both low power consumption and high durability
3Reliability
If the heating resistor element layer is made thick to improve step coverage, then durability is enhanced, but the resistance value increases leading to higher power consumption
Solution Approach 1:
The patent changes the surface topology parameter of the insulation layer through CMP flattening and selective etching, transforming it from a non-uniform surface with corner portions to a smooth, flattened surface with recessed portions. This parameter change allows the heating resistor element layer to be formed with optimal thickness that provides sufficient step coverage and durability while maintaining low resistance and power consumption
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 substrate achieves high durability and efficient thermal energy application with the heating resistor element layer formed on a smooth surface, preventing oxidation and maintaining low power consumption, as demonstrated by the thermal stress durability evaluation showing no fracture even at high pulse numbers.
Implementation Method 1
a surface including the intermediate insulation layer, the through-hole section, and the second electrode wiring layer is flattened using a chemical-mechanical polishing (CMP) method
Implementation Method 2
heating resistor elements for discharging liquid
Data Source
AI summary
A liquid-discharging-head substrate includes an insulation layer, an electrode, and a heating resistor element, wherein the insulation layer includes a first opening portion including a first opening formed in a surface of the insulation layer, a second opening having a smaller opening area than an opening area of the first opening, and a surface connecting the first opening and the second opening, and a second opening portion extending from the second opening to a back surface of the insulation layer, wherein the electrode is formed in the second opening portion, and a surface of the electrode is exposed from the second opening when viewed from the surface side of the insulation layer, and wherein the heating resistor element is in contact with the surface connecting the first opening and the second opening, and with the surface of the electrode.