Terminal Structure with Protruding Metal Layer for Piezoelectric Bonding
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Solution Overview
Problem
The existing terminal structures for connecting a flexure to a piezoelectric element in head suspensions are unstable in electrical connection and weak in bonding strength due to limited adhering areas, leading to potential breakage under stress and inferior adhesive failure.
Innovation Solution
A terminal structure with a metal layer, insulating layer, and wiring layer, where the insulating layer has a through hole allowing a conducting part to connect the wiring and metal layers, and the entire metal layer surface serves as a terminal face bonded to the piezoelectric element's electrode using a conductive adhesive, expanding the connection area for stability and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal face is limited within the area of the wiring layer exposed in the through hole, then the structure is simple, but the adhering area is limited resulting in unstable electrical connection and insufficient bonding strength
Solution Approach 1:
The patent extends the terminal face from a two-dimensional limited area to a three-dimensional configuration that protrudes toward the piezoelectric element. This dimensional extension allows the terminal face to utilize the vertical space within the through hole, significantly increasing the adhering area without expanding the horizontal footprint, thus improving electrical connection stability while maintaining structural simplicity.
Solution Approach 2:
The terminal face is nested within the through hole structure, protruding toward the piezoelectric element while being surrounded by the insulating layer and wiring layer. This nested configuration allows the terminal face to be contained within the existing structural boundaries while extending its effective bonding area, resolving the contradiction between reliability and complexity.
2Strength
If the terminal face is limited within the area of the wiring layer exposed in the through hole, then the manufacturing process is simple, but the bonding strength is insufficient leading to adhesive failure
Solution Approach 1:
The terminal face protrudes in the vertical dimension toward the piezoelectric element, transforming from a planar two-dimensional surface to a three-dimensional configuration. This dimensional change increases the adhering area available for bonding with the conductive adhesive, thereby enhancing bonding strength while maintaining manufacturing simplicity as the protrusion can be formed during standard terminal fabrication processes.
Solution Approach 2:
The terminal face is designed with localized protrusion specifically in the region where bonding with the piezoelectric element occurs. This local quality enhancement concentrates the bonding area where it is most needed, improving bonding strength without requiring complex modifications to the entire terminal structure, thus preserving ease of manufacture.
3Reliability
If stress is applied to the terminal face and conductive adhesive, then the electrical connection may break, but removing the stress allows resumption of connection, indicating instability
Solution Approach 1:
The terminal face protrudes in the vertical dimension toward the piezoelectric element, creating a three-dimensional bonding interface. This dimensional extension increases the adhering area and distributes stress more effectively across the bonding interface, preventing breakage under stress and ensuring stable electrical connection, thereby resolving the instability issue.
Solution Approach 2:
The protruding terminal face configuration is designed beforehand to provide enhanced bonding area and stress distribution capability. This pre-engineered structural feature acts as a cushioning mechanism that prevents adhesive failure under stress conditions, ensuring reliable electrical connection without requiring additional protective measures.
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 configuration stabilizes electrical connections and enhances bonding strength between the terminal face and conductive adhesive, ensuring reliable operation under stress and improving the overall performance of the head suspension.
Implementation Method 1
a terminal face defined on a surface of the metal layer and bonded through the conductive bonding part to the electrode of the piezoelectric element
Implementation Method 2
the piezoelectric element deforms in proportion to a voltage applied thereto, to minutely move the magnetic head at the front end of the load beam in a sway direction
Data Source
AI summary
A terminal structure includes an insulating layer hole formed through an insulating layer, a ground via that passes through the insulating layer hole and electrically connects a wiring layer formed on the insulating layer and a metal layer formed under the insulating layer to each other, and a terminal face defined on a surface of the metal layer and bonded through a conductive adhesive to an electrode of a piezoelectric element.