Liquid Ejection Head Substrate Cutting via Backside Laser Refractive Modification
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Solution Overview
Problem
The existing methods for manufacturing liquid ejection head substrates face challenges in accurately cutting the substrates while efficiently focusing a laser beam, due to the high density of ejection elements on the front surface and increased surface roughness on the back surface, which affects the formation of a reformed region inside the substrate.
Innovation Solution
The method involves etching the substrate from the back surface to form a recess with high flatness, allowing for precise focusing of a laser beam from the front surface to create a reformed portion inside the substrate, enabling accurate cutting of the substrate into individual pieces with reduced manufacturing load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser beam is focused into silicon substrate to reform the interior and then external force is applied to cause cracks, then substrate cutting is achieved, but cutting accuracy deteriorates due to high density of ejection elements on front surface and increased surface roughness on back surface
Solution Approach 1:
The patent inverts the conventional approach by forming the reformed region through laser irradiation from the back surface (second surface) rather than the front surface (first surface). This inversion allows the laser beam to focus accurately on the cutting line without being obstructed by the high-density ejection elements on the front surface, thereby improving both cutting accuracy and efficiency
Solution Approach 2:
The patent applies preliminary action by forming the reformed region inside the substrate before applying external force to cause cracks. The laser beam irradiates the back surface to create a reformed region along the intended cutting line, and only then is external force applied to propagate cracks through the substrate along this pre-formed reformed region, ensuring accurate cutting
2Productivity
If ejection elements are fabricated at high density on front surface, then productivity is improved, but laser beam focusing accuracy deteriorates
Solution Approach 1:
The patent resolves this contradiction by inverting the laser irradiation direction to the back surface, where no ejection elements are present. This allows the laser beam to focus with high accuracy on the cutting line without being blocked or scattered by the high-density ejection elements on the front surface, maintaining both high element density and laser focusing accuracy
3Ease of operation
If back surface is used for laser irradiation, then access to substrate interior is improved, but surface roughness increases causing poor laser focusing
Solution Approach 1:
The patent applies preliminary action by performing surface treatment on the back surface before laser irradiation. The back surface is treated to reduce surface roughness and improve flatness in the region where laser beam irradiation will occur, thereby enabling accurate laser focusing while maintaining the advantage of back-surface access
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 allows for high-yield, accurate cutting of liquid ejection heads by efficiently focusing the laser beam and forming a reformed region with high positional accuracy, thereby improving the manufacturing process efficiency.
Implementation Method 1
a step for irradiating a laser beam toward the first surface from the etched surface of the recess so as to form a reformed portion inside the substrate
Implementation Method 2
a step for etching a substrate, which has the energy generating element on a first surface, from a second surface, which is a surface on the opposite side from the first surface, thereby to form at a time at least a part of the liquid supply port and a recess along a cutting section of the substrate
Data Source
AI summary
A method for manufacturing a liquid ejection head substrate, including: (1) a step for etching a substrate, which has an energy generating element at a side of a first surface, from a side of a second surface, which is a surface on the opposite side from the first surface, thereby to form at a time at least a part of a liquid supply port and a recess along a cutting section of the substrate; (2) a step for irradiating a laser beam toward the side of first surface from the etched surface of the recess so as to form a reformed portion inside the substrate; and (3) a step for cutting the substrate at the reformed portion.