Fin-Shaped Heater Stack for Inkjet Printheads
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Solution Overview
Problem
Current inkjet printer technologies are thermally limited, leading to inefficient energy use and reliability issues due to the constraints of heater dimension and material waste, which hinder the achievement of small droplet sizes and high print speeds.
Innovation Solution
A vertical fin-shaped heater stack design that reduces heater dimension as a limiting factor, increases density, and minimizes thermal loss, featuring a substrate with perpendicular side surfaces and a protective overcoat to enhance reliability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If heater dimension is reduced to increase heater density, then heater pitch can be decreased, but heater reliability deteriorates due to water hammer and cavitation forces damaging thin layers
Solution Approach 1:
The heater stack transitions from a planar two-dimensional structure to a three-dimensional vertical fin-shaped structure. This dimensional change allows the heater to achieve high density through vertical stacking while maintaining sufficient structural thickness for reliability, as the vertical fins provide structural strength against water hammer and cavitation forces while occupying minimal horizontal space
Solution Approach 2:
The heater stack employs multiple layered materials including silicon substrate, silicon dioxide, silicon nitride, and metal layers forming a composite structure. This composite construction provides both the thermal functionality needed for heating and the mechanical strength required to withstand water hammer and cavitation forces, resolving the reliability issue while maintaining reduced heater dimension
2Use of energy by moving object
If heater area is increased to maintain adequate drop velocity, then energy transfer to ink improves, but thermal management deteriorates due to extreme heat generated on the chip
Solution Approach 1:
The heater structure is segmented into multiple vertical fin elements rather than a single large planar heater. This segmentation allows distributed heat generation across multiple smaller heating zones, improving energy transfer efficiency to ink droplets while the vertical orientation and spacing facilitate better thermal management by reducing heat accumulation on the chip substrate
Solution Approach 2:
By transitioning to vertical fin-shaped heaters, the heating surface is oriented perpendicular to the chip substrate. This dimensional change reduces the heater's footprint on the chip while maintaining adequate heating area through vertical extension, thereby improving energy transfer to ink without generating excessive heat on the chip that would compromise thermal management
3Area of moving object
If heater pitch is decreased to increase heater density, then more heaters can be packed, but manufacturing precision deteriorates due to difficulty in forming flow features and chamber walls
Solution Approach 1:
The heater structure transitions from planar to vertical fin-shaped configuration. This dimensional change allows heaters to be packed more densely in the horizontal plane while the vertical fins provide sufficient space above and below for forming flow features and chamber walls, thereby increasing heater density without compromising manufacturing precision for fluidic structures
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 vertical fin-shaped heater stack improves ejector efficiency, reduces water hammer and cavitation forces, and allows for smaller inkjet drop sizes and higher print speeds while maintaining competitive thermal management.
Implementation Method 1
fluid heater elements responsive to repetitive electrical activation and deactivation to produce repetitive cycles of ejection of a fluid
Implementation Method 2
the area of underlying silicon substrate is also reduced and ink bubbles can form on both sides of the heater stack with minimum thermal loss to the surrounding substrate
Implementation Method 3
water hammer and cavitation forces on the heater stack surface are reduced due to the fact that the heater stack surface is disposed parallel to ink flow and jetting direction
Implementation Method 4
greatly reduces cavitation force due to bubble collapse
Data Source
AI summary
A fin-shaped heater stack includes first strata configured to support and form fluid heater elements responsive to repetitive electrical activation and deactivation to produce repetitive cycles of ejection of a fluid, and second strata on the first strata to protect the fluid heater elements from adverse effects of the repetitive cycles of fluid ejection and of contact with the fluid. The first strata include a substrate having a front surface, and heater substrata supported on the front surface. The heater substrata have opposite facing side surfaces which extend approximately perpendicular to the front surface and an end surface interconnecting the side surfaces which extends approximately parallel to the front surface such that the heater substrata is provided in either an upright or inverted fin-shaped configuration on the substrate with the fluid heater elements forming the opposite facing side surfaces of the heat substrata.