Piezoelectric Ceramic Device Protrusion Solder Control
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Solution Overview
Problem
The existing piezoelectric devices face issues with solder adherence and electrical short circuits due to excessive solder usage, which affects the voltage-displacement characteristics and reliability of the device.
Innovation Solution
The ceramic device incorporates protrusions on the side electrodes and interspersed exposed ceramic regions on the surface electrodes with lower wettability to solder, preventing solder overflow and reducing electrical short circuits while maintaining high adhesion and bondability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder is used to join side electrodes to substrates, then electrical connection and mechanical bonding are achieved, but solder may ride over upper end surfaces of side electrodes and enter surfaces of surface electrodes, causing adverse effects on voltage-displacement characteristics and electrical short circuits
Solution Approach 1:
The patent applies local quality by creating a protrusion at the upper end surface of the side electrode that is composed of the same material as the side electrode, while the surface electrode material has different wettability characteristics. This local structural modification (protrusion) changes the solder flow behavior locally, preventing solder from entering the surface electrode region while maintaining good electrical connection at the side electrode-substrate interface.
Solution Approach 2:
The protrusion structure creates an asymmetric geometry at the side electrode upper end surface. This asymmetric shape (protrusion extending from the side electrode surface) disrupts the symmetric flow path of solder, causing solder to preferentially wet the side electrode material of the protrusion rather than entering the surface electrode region, thus preventing solder overflow into sensitive areas.
2Strength
If solder adheres to surface electrodes, then mechanical bonding is achieved, but expansion and contraction of surface electrodes are restricted at application of voltage, adversely affecting voltage-displacement characteristics
Solution Approach 1:
The protrusion structure creates a localized region of high solder adhesion at the side electrode upper end surface, concentrating the bonding function in this specific area. This local quality modification ensures that solder adheres strongly to the side electrode (providing mechanical bonding) while preventing solder from adhering to the surface electrode, thereby maintaining the surface electrode's freedom to expand and contract under voltage.
Solution Approach 2:
The invention extracts the bonding function from the surface electrode region and relocates it to the side electrode protrusion region. By taking out the solder adhesion function from the surface electrode area and concentrating it in the side electrode protrusion area, the surface electrode remains free from solder restriction, preserving voltage-displacement characteristics while still achieving mechanical bonding through the side electrode-substrate connection.
3Quantity of substance
If excessive solder enters the gap between surface electrodes, then filling is achieved, but electrical short circuits occur between surface electrodes
Solution Approach 1:
The protrusion structure creates a local quality difference in material wettability, where the side electrode material (protrusion) has high solder wettability and the surface electrode material has low solder wettability. This local differentiation causes solder to be confined to the side electrode region and prevents it from entering the gap between surface electrodes, maintaining electrical insulation while still achieving adequate solder filling for mechanical bonding.
Solution Approach 2:
The protrusion acts as an intermediary structure between the side electrode and the surface electrode region. It serves as a mediator that captures and retains solder, preventing solder from directly contacting and bridging the gap between surface electrodes. The protrusion material properties mediate the solder flow behavior, ensuring solder is stopped at the side electrode protrusion and does not proceed to cause short circuits.
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 enhances the reliability of electrical connections, suppresses adverse effects on voltage-displacement characteristics, and increases mechanical strength by controlling solder expansion and contraction.
Implementation Method 1
a surface of a ceramic material having lower wettability to a conductive joining material than a material for the surface electrode is exposed
Data Source
AI summary
A piezoelectric device is a fired body including a body part 10 and external electrodes 21 and 22. A surface of the side electrode 22 is comprised only of a material for the side electrode 22. On a surface of the surface electrode 21 or a surface of a connection portion where the surface electrode 21 and the side electrode 22 are connected to each other, a protrusion h extending along a direction along which the connection portion extends and sticking out in a thickness direction of the surface electrode 21 is provided. A region, on the surface of the surface electrode 21, farther from the connection portion than the protrusion h is interspersed with a plurality of exposed portions in each of which a surface of a ceramic material having lower solder wettability than a material for the surface electrode 21 is exposed.