Piezoelectric Substrate Electrode Segmentation for Joining Strength
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Solution Overview
Problem
The piezoelectric substrate used in liquid discharge heads faces issues with low joining strength due to differences in planar and cross-sectional shapes between individual and surface electrodes, leading to weak connections and misalignment during manufacturing, which affects the reliability of electrical connections.
Innovation Solution
The solution involves enhancing the bonding strength by making electrical connections at a small-width portion of the second electrode and ensuring that the surface electrode for the common electrode has a larger width to accommodate misalignment, with the electrical connection between the second and third electrodes occurring at a connection portion with a larger width than the small-width portion on the second electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the surface electrode for the common electrode is made large enough to accommodate misalignment, then manufacturing reliability is improved, but joining strength with the outside becomes low
Solution Approach 1:
The surface electrode is divided into two functional regions: a large-width connection portion for accommodating misalignment and ensuring reliable electrical connection, and a small-width portion for providing strong joining strength with the outside. This segmentation allows each region to optimize for its specific function without compromising the other.
Solution Approach 2:
Different portions of the surface electrode are given different width characteristics to fulfill different requirements. The connection portion has large width for reliability, while the portion for external connection has small width for strength. This local differentiation resolves the contradiction between overall reliability and localized joining strength.
2Ease of manufacture
If via holes are formed before firing, then ease of manufacture is improved, but misalignment occurs due to dimensional variation, worsening manufacturing precision
Solution Approach 1:
The via holes are formed in advance before the firing process, when the piezoelectric ceramic layer is in its green sheet state and easier to process. This preliminary action simplifies the manufacturing process, while the subsequent firing and the design of the enlarged connection portion compensate for any alignment variations that occur.
3Reliability
If the surface electrode for the common electrode is made large to compensate for misalignment, then electrical connection reliability is improved, but the joining strength between the electrode and outside becomes low
Solution Approach 1:
The surface electrode is divided into two functional regions: a large-width connection portion for accommodating misalignment and ensuring reliable electrical connection, and a small-width portion for providing strong joining strength with the outside. This segmentation allows each region to optimize for its specific function without compromising the other.
Solution Approach 2:
Different portions of the surface electrode are given different width characteristics to fulfill different requirements. The connection portion has large width for reliability, while the portion for external connection has small width for strength. This local differentiation resolves the contradiction between overall reliability and localized joining strength.
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 reduces the likelihood of disconnection due to misalignment and enhances the overall joining strength between electrodes, leading to a more reliable electrical connection and improved performance of the liquid discharge head.
Implementation Method 1
The piezoelectric ceramic layer may deform and pressurize a liquid in the pressurizing chambers by applying a voltage to between the first electrodes and the second electrode
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
The present invention aims at providing a piezoelectric substrate with high joining strength between an electrode of the piezoelectric substrate, particularly an electrode for a common electrode and the outside, as well as an assembly, a liquid discharge head, and a recording device, each of which uses the piezoelectric substrate. The piezoelectric substrate of the present invention is a flat plate-shaped piezoelectric substrate including a piezoelectric ceramic layer 21b, a plurality of first electrodes 24 and a second electrode 28 disposed on one main surface of the piezoelectric ceramic layer 21b, a third electrode 24 disposed on the other main surface of the piezoelectric ceramic layer 21b so as to oppose to the first electrodes 25, and a through-conductor 34 electrically connecting the second electrode 28 and the third electrode 24. The second electrode 28 includes a connection portion 28a connected to the through-conductor 3, and a small-width portion 28b having a smaller width than the connection portion 28a when the piezoelectric substrate is viewed from above. The second electrode 28 and the outside are electrically connected to each other at the small-width portion 28b.