Acoustic Wave Electrode Layout for ESD and Piston Mode Stability
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Solution Overview
Problem
Acoustic wave devices with interdigital transducer electrodes suffer from surge breakdown due to electrostatic discharge (ESD) and interference with piston mode, particularly in the outer busbar portions adjacent to metal reflectors with different potentials.
Innovation Solution
The design includes a piezoelectric body with interdigital transducer electrodes and reflectors, where the interdigital transducer electrodes have busbars and electrode fingers with specific width configurations and positioning to reduce ESD tolerance and prevent interference with piston mode by optimizing the placement and shape of busbar portions relative to electrode fingers and reflectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer busbar portions are located adjacent to metal material portions such as reflectors with different potentials, then the acoustic wave device can achieve proper electrical connection and structural integrity, but surge breakdown occurs due to electrostatic discharge (ESD) in the outer busbar portions
Solution Approach 1:
An insulating film is introduced as an intermediary layer between the outer busbar portion and the adjacent metal reflector. This insulating film prevents direct electrical contact between components at different potentials, thereby blocking the ESD path while maintaining the structural arrangement. The insulating film acts as a mediator that allows the busbar to remain positioned for proper electrical connection without suffering from surge breakdown.
Solution Approach 2:
The potential harmful ESD between adjacent metal portions at different potentials is converted into a beneficial protective mechanism. By intentionally introducing an insulating film, the design transforms what would be a dangerous electrical discharge path into a controlled insulation barrier, preventing surge breakdown while maintaining the necessary electrical connections through other pathways.
2Stability of the object's composition
If wide portions are provided in both of the first electrode fingers and the second electrode fingers, then the piston mode can be formed to suppress transverse-mode ripple, but the outer busbar portions become vulnerable to ESD due to proximity with metal reflectors
Solution Approach 1:
The insulating film is applied selectively to specific locations where ESD risk exists, rather than uniformly across the entire device. The insulating film is positioned at the outer busbar portions adjacent to metal reflectors, providing localized protection exactly where the contradiction between piston mode stability and ESD tolerance arises, without affecting other functional areas.
3Productivity
If the outer busbar portions are positioned for optimal acoustic wave transmission, then the piston mode is maintained, but the device becomes susceptible to surge breakdown from electrostatic discharge
Solution Approach 1:
The insulating film serves as a mediator that allows the outer busbar portions to maintain their optimal positioning for acoustic wave transmission while preventing ESD. The film enables the busbar to remain in the position required for piston mode maintenance and acoustic efficiency, but blocks the harmful electrical discharge pathway to adjacent metal reflectors.
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
Significantly improves ESD tolerance while reducing or preventing interference with piston mode, enhancing the operational stability and reliability of the acoustic wave devices.
Implementation Method 1
an acoustic wave device that includes a piezoelectric substrate (piezoelectric body portion) and an interdigital transducer electrode provided on or above the piezoelectric substrate
Implementation Method 2
a reflector is formed on each side of the interdigital transducer electrode in a propagation direction of surface acoustic waves on the piezoelectric substrate
Data Source
AI summary
An acoustic wave device includes a piezoelectric body portion, an interdigital transducer electrode connected to a first terminal and a second terminal, and a reflector connected to the second terminal. In the interdigital transducer electrode, in the interdigital transducer electrode, where, of a group of electrode fingers, the electrode finger located at one end in a second direction is a first end electrode finger and the electrode finger located at another end is a second end electrode finger, the first end electrode finger is located between the reflector and the second end electrode finger in the second direction. An outer busbar portion of one of a first busbar and a second busbar, not connected to the first end electrode finger, is located on an inner side in the second direction relative to a center portion, in a first direction, of the first end electrode finger.