Droplet Deposition Head Multilayer Passivation Coating
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Solution Overview
Problem
Existing droplet deposition heads face issues with fluid penetration and electrode corrosion due to inadequate passivation coatings, particularly in high-aspect-ratio fluid chambers, leading to reduced operational lifetime and inefficiencies in inkjet printheads.
Innovation Solution
A passivation coating comprising a laminate of an inorganic insulating layer deposited by atomic layer deposition and an organic insulating layer by plasma-enhanced chemical vapor deposition, with misaligned defects at the interface, providing a longer pathway for ionic species migration and improved resistance to field-driven penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer passivation coating is used on electrodes in high-aspect-ratio fluid chambers, then the coating process is simple, but fluid penetration and electrode corrosion occur leading to reduced operational lifetime
Solution Approach 1:
The patent applies a composite passivation coating consisting of multiple layers with different materials and properties. The first layer is an inorganic insulating layer deposited by atomic layer deposition, and the second layer is an organic insulating layer deposited by plasma-enhanced chemical vapor deposition. This composite structure provides superior protection against fluid penetration and electrode corrosion compared to single-layer coatings, thereby extending operational lifetime while managing the increased structural complexity.
Solution Approach 2:
The passivation coating is segmented into multiple distinct layers, each with specific functions. The first inorganic layer provides a dense barrier against ionic species, while the second organic layer provides additional protection and chemical resistance. This segmentation allows each layer to optimize its protective function, preventing fluid penetration and corrosion that would occur with a single-layer coating.
2Volume of moving object
If the fluid chamber has a high aspect ratio, then the droplet deposition head can be compact, but the passivation coating becomes inadequate allowing fluid penetration
Solution Approach 1:
The composite passivation coating structure is specifically designed to address the challenges of high-aspect-ratio fluid chambers. The combination of inorganic and organic insulating layers creates a multi-barrier system that is highly effective at preventing fluid penetration even in compact, high-aspect-ratio chamber geometries where coating uniformity and effectiveness are difficult to achieve.
Solution Approach 2:
The patent transitions from a single-layer coating approach to a multi-layer coating approach, adding dimensional complexity to the passivation structure. This dimensional change from one layer to multiple layers provides enhanced protection against fluid penetration in high-aspect-ratio chambers by creating multiple barriers that ionic species must traverse.
3Reliability
If a thicker passivation coating is used to prevent fluid penetration, then corrosion resistance improves, but the coating thickness increases reducing chamber space
Solution Approach 1:
The composite coating structure achieves superior corrosion resistance with optimized total thickness by combining materials with different protective properties. The inorganic layer provides a dense barrier with excellent adhesion, while the organic layer provides chemical resistance and additional barrier properties. This composite approach achieves better protection per unit thickness compared to single-layer coatings, maintaining chamber space while improving corrosion resistance.
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 multilayer passivation coating significantly enhances the operational lifetime of droplet deposition heads by preventing fluid penetration and corrosion, allowing for the use of a wider variety of fluids across a broader pH range and higher ion conductivity.
Implementation Method 1
a passivation coating which comprises, at least in part, a laminate comprising an inorganic insulating layer nearest to or contacting an electrode and an organic insulating layer overlying the inorganic insulating layer
Implementation Method 2
a passivation coating which comprises, at least in part, a laminate comprising an inorganic insulating layer nearest to or contacting an electrode and an organic insulating layer overlying the inorganic insulating layer
Implementation Method 3
a piezoelectric actuator element formed at least in part by a fluid chamber wall having an electrode thereon, which element is displaceable in response to a drive voltage to generate a pressure in the chamber
Data Source
AI summary
A droplet deposition head having a fluid chamber connected to a droplet ejection nozzle and to a reservoir for the fluid, and a piezoelectric actuator element formed at least in part by a fluid chamber wall having an electrode thereon, which element is displaceable in response to a drive voltage to generate a pressure in the chamber to eject a droplet of fluid from the chamber through the nozzle wherein the electrode is provided with a passivation coating which comprises, at least in part, a laminate comprising an inorganic insulating layer nearest to or contacting the electrode and an organic insulating layer overlying the inorganic insulating layer wherein defects in the insulating layers tend to be misaligned at the interface there between and wherein the inorganic insulating layer has thickness less than or equal to 500 nm and the organic insulating layer has a thickness less than 3 μm.