Silicon Acoustic Wave Substrate Laser Protection
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Solution Overview
Problem
Acoustic wave devices with IDT electrodes sealed by resin face challenges in reducing height due to the need for thick resin layers to prevent laser damage, as traditional materials like lithium tantalate and lithium niobate transmit laser light, requiring bottomed holes that increase resin thickness.
Innovation Solution
Using a silicon-based acoustic wave substrate with a multilayer structure including high-velocity and low-velocity layers, where silicon reduces laser transmission, allowing for through-holes in the resin that display information without needing bottomed holes, thus minimizing resin thickness and preventing laser damage to IDT electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional acoustic wave substrates (lithium tantalate or lithium niobate) are used, then the substrate is transparent or translucent allowing laser light transmission, but this causes laser light to reach and damage the IDT electrodes when holes are provided in the sealing resin
Solution Approach 1:
A silicon-based layer is introduced as an intermediary between the sealing resin and the IDT electrodes. This silicon layer acts as a mediator that blocks laser light transmission while allowing the holes to be provided through the sealing resin for information display, thus preventing laser damage to the IDT electrodes without compromising the ease of hole formation
Solution Approach 2:
The acoustic wave substrate is constructed as a composite structure combining traditional piezoelectric materials (lithium tantalate or lithium niobate) with a silicon-based layer. This composite material configuration maintains the acoustic wave functionality while the silicon component provides laser light blocking capability, resolving the contradiction between transparency for hole formation and opacity for laser protection
2Reliability
If bottomed holes are provided in the sealing resin to prevent laser transmission, then laser damage to IDT electrodes is prevented, but the thickness of the sealing resin must be increased, making it difficult to reduce device height
Solution Approach 1:
The silicon-based layer serves as a laser-blocking intermediary positioned between the sealing resin and IDT electrodes. This allows the use of through-holes rather than bottomed holes, as the silicon layer prevents laser transmission even when holes extend through the entire sealing resin thickness, thereby reducing the required sealing resin thickness and device height while maintaining protection reliability
Solution Approach 2:
The laser-blocking function is extracted from the sealing resin and assigned to a dedicated silicon-based layer. This separation of functions allows the sealing resin to be optimized for its primary sealing purpose with minimal thickness, while the silicon layer independently provides the laser protection function, resolving the contradiction between protection reliability and device height
3Length of stationary object
If the sealing resin thickness is reduced to decrease device height, then smaller electronic apparatuses can be achieved, but the ability to prevent laser light from reaching IDT electrodes is compromised
Solution Approach 1:
The acoustic wave substrate uses a composite structure with a silicon-based layer integrated into the substrate or as a separate layer between the sealing resin and IDT electrodes. This composite configuration provides inherent laser blocking capability that is independent of sealing resin thickness, enabling thin sealing resin design for reduced device height while maintaining laser protection
Solution Approach 2:
The silicon-based layer acts as a permanent intermediary laser barrier that does not depend on sealing resin thickness. This mediator ensures laser light is blocked regardless of how thin the sealing resin is made, resolving the contradiction between device height reduction and laser protection capability
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 enables a smaller acoustic wave device height by eliminating the need for thick resin layers and reduces the risk of laser damage to IDT electrodes, while enhancing visibility of displayed information through colored and recessed through-holes.
Implementation Method 1
the acoustic wave substrate is made of silicon or includes a layer made of silicon... When laser light is applied to the top surface of the sealing resin 104, holes are provided therein... the acoustic wave substrate 101 made of lithium tantalate (LiTaO3) is transparent or translucent. Therefore, when laser light is applied to the acoustic wave substrate 101, the acoustic wave substrate 101 transmits the laser light
Implementation Method 2
an acoustic wave substrate including a first main surface and a second main surface that are opposite each other, an IDT electrode provided on the first main surface... The acoustic wave substrate is made of silicon or includes a layer made of silicon
Data Source
AI summary
An acoustic wave device includes an acoustic wave substrate including a first main surface and a second main surface, IDT electrodes provided on the first main surface, and sealing resin covering at least the second main surface of the acoustic wave substrate. A hollow is provided in a region where the IDT electrodes on the first main surface of the acoustic wave substrate is located. The sealing resin has through-holes each extending from a top surface 13B of the sealing resin to the second main surface of the acoustic wave substrate. The acoustic wave substrate is made of silicon or includes a layer made of silicon.