Thermal Inkjet Printhead Nozzle Density via Dielectric Segmentation
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Solution Overview
Problem
High nozzle density thermal inkjet printheads face challenges in accommodating return traces and ground planes due to insufficient room, leading to reduced ink refill speed and increased topography in dielectric layers, which can result in cracking and reliability issues.
Innovation Solution
The design incorporates separate openings in the dielectric layer for each resistor column, using a combination of directional and wet etch processes to maintain proximity between thermal resistors and ink feed slots, allowing for increased nozzle density and reduced refill time while protecting vias from ink and chemicals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If separate openings in dielectric layer are used for each resistor column, then proximity between thermal resistors and ink feed slots is maintained and refill time is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The dielectric layer is segmented into multiple separate openings, each aligned with a specific resistor column. This segmentation allows independent access to each resistor column from the ink feed slots, enabling simultaneous ink refilling for multiple nozzles without interference, thus maintaining high nozzle density while ensuring adequate ink supply to each thermal resistor
Solution Approach 2:
The patent introduces a vertical dimension by creating openings through the dielectric layer to establish direct vertical pathways between the ink feed slots and the resistor columns. This dimensional change eliminates the need for lateral trace routing, maintaining close proximity between thermal resistors and ink feed slots while avoiding topography issues in the dielectric layer
2Manufacturing precision
If high nozzle density is implemented, then printing resolution is improved, but room for return traces and ground planes becomes insufficient
Solution Approach 1:
The patent transitions electrical connections from a planar two-dimensional layout to a three-dimensional structure by forming vias through the dielectric layer. This allows return traces and ground planes to be positioned in different vertical layers rather than competing for horizontal space, enabling high nozzle density while accommodating all necessary electrical routing
Solution Approach 2:
The patent nests multiple functional layers within a compact vertical structure: the dielectric layer with its openings, the resistor columns, the ink feed slots, and the electrical trace layers are arranged in a nested configuration where each layer serves its function without interfering with others, maximizing space utilization for both high nozzle density and adequate electrical routing
3Reliability
If directional and wet etch processes are used to create openings, then precision and reliability are improved, but manufacturing complexity increases
Solution Approach 1:
The etching process is segmented into two distinct stages: directional etching to create initial openings with precise alignment, followed by wet etching to complete the openings and remove remaining dielectric material. This segmented approach ensures that each etching step performs its specific function optimally, achieving high precision and reliability while keeping the overall process manageable through clear separation of tasks
Solution Approach 2:
The directional etching process performs preliminary action by creating precisely aligned openings in the dielectric layer before the wet etching step. This preliminary structuring ensures that subsequent wet etching only needs to complete the openings, reducing the risk of misalignment and improving overall precision while making the manufacturing process more controllable and reliable
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 the reliability and accuracy of thermal inkjet printheads by maintaining close proximity between thermal resistors and ink feed slots, reducing refill time, and preventing topography-related issues, thus improving overall performance.
Implementation Method 1
each including a thermal resistor formed in a resistive layer
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The present disclosure includes a method of fabricating a thermal ink jet printhead including depositing a first metal layer having a thickness to form a power bus, depositing a first dielectric layer, forming a via in the first dielectric layer to connect the first metal layer to a second metal layer, depositing the second metal layer, depositing a resistive layer, forming a thermal resistor in the resistive layer, depositing a second dielectric layer, and removing a portion of the second dielectric layer.