Acoustic Wave Filter Electrode Layout for Heat Dissipation
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Solution Overview
Problem
Bulk acoustic wave devices with air cavities experience temperature gradients and reduced power capacity under high power due to inefficient heat dissipation, leading to resonance frequency variations and decreased performance.
Innovation Solution
The acoustic wave device incorporates a substrate with air cavities, hanging bridges, and via holes in the upper electrode layer, which reduces temperature gradients and enhances heat transfer by creating a ring-shaped effective resonance region, thereby improving power capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the area of the acoustic wave device is increased to reduce power dissipation per unit area, then the power capacity is improved, but the device size increases
Solution Approach 1:
The upper electrode layer is segmented into multiple regions separated by hanging roofs, creating multiple resonance regions. This segmentation allows heat to be dissipated across multiple smaller areas rather than one large area, improving power capacity without proportionally increasing device footprint
Solution Approach 2:
The patent introduces vertical hanging roofs that extend from the upper electrode layer into the air cavity, creating a three-dimensional heat dissipation structure. This vertical dimension provides additional heat transfer pathways without significantly increasing the planar device area
2Temperature
If multiple grounding points or cooling means are provided at the peripheral of the hottest resonator, then heat dissipation is improved, but the effect is limited due to difficulties in transmitting power of the FBAR acoustic wave to a surrounding region
Solution Approach 1:
The hanging roofs act as intermediary structures that extend the heat dissipation pathway from the hot resonance region to the cooler peripheral regions. These roofs provide a thermal conduction pathway that bridges the temperature gradient without interfering with the acoustic wave transmission
Solution Approach 2:
The hanging roofs are extracted as separate structural elements that perform the specific function of heat dissipation, while the main resonance structure remains intact for efficient power transmission. This separation allows optimized heat management without compromising acoustic performance
3Reliability
If the internal temperature gradient is reduced, then the filtering performance is improved, but the power capacity cannot be sufficiently increased under high power conditions
Solution Approach 1:
The hanging roofs are strategically positioned to create localized heat dissipation zones at critical hot spots within the device. This local quality approach addresses temperature gradients where they are most severe, maintaining filtering performance while enabling higher power operation
Solution Approach 2:
The hanging roofs create dynamic heat dissipation pathways that adapt to the thermal load. Under high power conditions, the thermal conduction through the hanging roofs becomes more significant, automatically providing enhanced cooling where and when it is most needed
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
The solution effectively suppresses temperature gradients and increases power capacity by shortening the distance from the resonance area to the edge, reducing energy coupling, and enhancing the Q value, resulting in improved filtering performance.
Implementation Method 1
a piezoelectric layer, and an upper electrode layer, which are sequentially stacked from bottom to top
Implementation Method 2
the BAW device having the air cavity (e.g., a film bulk acoustic resonator, FBAR) can transfer generated heat from the piezoelectric layer to the substrate
Implementation Method 3
the resonance region occurs in the piezoelectric layer
Data Source
AI summary
An acoustic wave device and a filter. The acoustic wave device comprises: a substrate, a lower electrode layer, a piezoelectric layer, and an upper electrode layer, which are sequentially stacked from bottom to top, where at least one air cavity is disposed in the substrate at a region corresponding to the upper electrode layer, and at least one of: a first hanging bridge is located at a portion of the upper electrode layer which connects to outside, first hanging roofs are located at an edge and an inner portion of the upper electrode layer, and at least one via hole runs through one of the first hanging roofs which is located at the inner portion of the upper electrode layer; a quantity of the at least one air cavity is greater than one; or the upper electrode layer has a recess extending along a horizontal direction.