Discharge Head Electrode Sulfide Coating Brazing Control
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Solution Overview
Problem
The existing methods for connecting discharge driving elements to a wired board in discharge heads, such as ink-jet heads, face issues with conductive brazing materials causing inhibition of piezoelectric element deformation, increased resistance, electric disconnection, and short circuits, due to their high fluidity and affinity for metal surfaces.
Innovation Solution
A discharge head design featuring a silver sulfide coating on the surface of the individual electrodes, except for the connecting sections, which are made of a metal that is hardly sulfurized, such as gold, to prevent excessive conductive brazing material from adhering to non-connecting areas and ensure reliable mechanical and electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive brazing material is used to connect terminals to surface electrodes, then reliable electrical connection is achieved, but the melted brazing material moves to pressure chamber areas and inhibits piezoelectric element deformation
Solution Approach 1:
The patent applies different surface treatments to different regions of the surface electrode: the connecting portion (where brazing occurs) is left with a metal surface that promotes brazing material adhesion, while the opposing surface (facing the pressure chamber) is coated with a material that repels brazing material. This local differentiation allows the brazing material to stay confined to the connecting area and prevents it from migrating to the pressure chamber area where it would inhibit piezoelectric element deformation.
2Reliability
If conductive brazing material is used for connection, then electrical connectivity is established, but metal diffusion increases resistance and may cause electric disconnection
Solution Approach 1:
The patent introduces a specially treated surface coating on the surface electrode that acts as an intermediary between the conductive brazing material and the metal surface. This coating layer prevents direct contact and diffusion between the brazing material and the electrode metal, thereby eliminating the metal diffusion problem that causes increased resistance and potential disconnection, while still maintaining reliable electrical connectivity through the brazed joint.
3Strength
If conductive brazing material is used, then mechanical strength of joint is improved, but short circuits may occur between adjoining joined portions
Solution Approach 1:
The patent creates a spatial differentiation in surface properties: the connecting portion has high affinity for brazing material to ensure strong mechanical bonding, while the opposing surface has low affinity to prevent brazing material migration. This local quality control confines the brazing material to specific areas, ensuring mechanical strength at joints while preventing short circuits between adjacent electrode connections.
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 design prevents the inhibition of piezoelectric element deformation, reduces connection resistance, and avoids short circuits, allowing for stable liquid droplet discharge performance without affecting ink discharge characteristics.
Implementation Method 1
A discharge head design featuring a silver sulfide coating on the surface of the individual electrodes, except for the connecting sections, which are made of a metal that is hardly sulfurized, such as gold
Implementation Method 2
the conductive brazing material is melted by being heated
Data Source
AI summary
A discharge head includes a discharge driving element; an individual electrode formed on the discharge driving element and having a connecting section; and a wired board having a terminal which is joined to the individual electrode by a conductive brazing material. The connecting section is provided to face the terminal, and a metal, which is hardly sulfurized, is exposed in a facing area, of a surface of the connecting section, facing the terminal. A silver sulfide coating is formed on a surface of the connecting section except for a portion facing the terminal. The silver sulfide coating has a low affinity for the conductive brazing material, which is hardly wetted thereby. Therefore, even when the conductive brazing material leaks, then the conductive brazing material is not retained on the silver sulfide coating, and no influence is exerted on the driving operation of the discharge head.