Piezoelectric Resonator Layout for Dense RF Filter Packaging
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Solution Overview
Problem
The increasing demand for miniaturization and power efficiency in mobile devices, particularly in radio-frequency filters for wireless communication systems, is challenging due to the need for processing multiple frequency bands, which existing piezoelectric element designs struggle to meet in terms of size and packaging density.
Innovation Solution
A piezoelectric element unit design that includes a substrate with a piezoelectric film and electrodes arranged to facilitate bulk acoustic wave propagation parallel to the substrate, allowing for increased film thickness and wider side surfaces, along with spacers and protective films to suppress damping and enhance packaging density, while maintaining efficient acoustic wave propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the piezoelectric element uses conventional design with acoustic wave propagation perpendicular to substrate, then the structure is simple, but the packaging density is low and device size is large
Solution Approach 1:
The patent changes the acoustic wave propagation direction from perpendicular to the substrate (conventional design) to parallel to the substrate (new dimension). This dimensional change allows the piezoelectric film thickness to be increased while maintaining a compact footprint, thereby reducing device size and improving packaging density without excessive structural complexity
Solution Approach 2:
The patent employs a composite structure consisting of a piezoelectric film, electrode films, and insulating films stacked together. This composite material approach enables the acoustic wave to propagate parallel to the substrate while maintaining structural integrity and electrical functionality, resolving the contradiction between compact size and structural complexity
2Reliability
If the piezoelectric film thickness is increased to improve electromechanical coupling, then the coupling coefficient increases, but the device area increases
Solution Approach 1:
By changing the acoustic wave propagation direction to parallel to the substrate, the patent decouples the relationship between film thickness and device area. This allows the piezoelectric film thickness to be increased for higher electromechanical coupling coefficients without proportionally increasing the device footprint area, as the thickness enhancement occurs in the vertical dimension rather than expanding the horizontal area
3Adaptability or versatility
If multiple frequency bands are processed in mobile devices, then communication capability improves, but the number of filters increases and packaging density decreases
Solution Approach 1:
The patent creates a piezoelectric element design that can be universally applied across multiple frequency bands. By enabling compact, high-density packaging through parallel acoustic wave propagation, the same element structure can be used for different RF filters handling various frequency bands (5G, 4G, Wi-Fi, etc.), allowing mobile devices to process multiple frequency bands without proportionally increasing overall device volume
Solution Approach 2:
The patent's compact piezoelectric element structure enables nested or closely packed arrangements of multiple filters within a small volume. The reduced footprint of each individual element allows multiple frequency band filters to be nested or tightly integrated, improving packaging density while maintaining the capability to process multiple frequency bands simultaneously
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 enables the miniaturization and high-density packaging of piezoelectric elements, reducing manufacturing costs and improving performance with high electromechanical coupling coefficients and temperature stability, suitable for both BAW and SAW applications.
Implementation Method 1
a piezoelectric element unit includes: a substrate having a main surface; a piezoelectric film arranged on the substrate
Implementation Method 2
a piezoelectric element unit includes: a substrate having a main surface; a piezoelectric film arranged on the substrate
Data Source
AI summary
A piezoelectric element unit includes: a substrate having a main surface; a piezoelectric film arranged on the substrate and having a first side surface, a second side surface opposite the first side surface, and a bottom surface that faces the main surface and is connected to the first side surface and the second side surface; a first electrode arranged on the substrate and in contact with the first side surface of the piezoelectric film; and a second electrode arranged on the substrate in contact with at least one of the first side surface and the second side surface of the piezoelectric film, and provided to be separated from the first electrode.