SAW Module Coating Layout to Prevent Edge Cracks and Exfoliation
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Solution Overview
Problem
Existing SAW modules face issues with coating layer exfoliation and crack generation due to SAW vibration, particularly on the end surface and corner portions of the piezoelectric element substrate, which compromises module durability.
Innovation Solution
A coating layer is applied to cover the front, end, and corner portions of the piezoelectric element substrate, with optimized thickness ranging from 600 nm to 1400 nm, using methods like CVD or ALD, and enhanced with hydrophilic properties to prevent exfoliation and crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating layer is formed on the piezoelectric element substrate to protect it, then durability is improved, but the coating layer may exfoliate or generate cracks due to SAW vibration
Solution Approach 1:
The patent optimizes the coating layer thickness to a specific range (600-1400 nm) to prevent exfoliation and crack generation during SAW vibration. This parameter optimization ensures the coating is thick enough to provide protection but thin enough to maintain flexibility and adhere to the substrate under vibrational stress
Solution Approach 2:
The coating layer is applied with different thicknesses at different locations: the front surface has thickness of 600-1400 nm, the end surface has thickness of 600 nm or more (50% or more of front surface thickness), and corner portions have thickness of 600 nm or more (50% or more of front surface thickness). This local quality variation provides enhanced protection at critical stress points while maintaining overall coating integrity
2Reliability
If the coating layer thickness is increased to improve protection, then durability is improved, but the coating layer becomes more prone to exfoliation due to SAW vibration
Solution Approach 1:
The patent identifies and applies an optimal thickness range (600-1400 nm) that balances protection effectiveness with adhesion strength. Within this range, the coating is sufficiently thick to protect the substrate but thin enough to flex with the substrate during SAW vibration, preventing exfoliation
Solution Approach 2:
Rather than applying a uniformly thick coating that would be too thick and brittle, the patent uses a partially thick coating (600-1400 nm) that provides sufficient protection without exceeding the threshold where the coating becomes too rigid and prone to exfoliation
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 coating layer exfoliation and crack generation, enhancing the durability of the SAW module by ensuring the coating layer adheres uniformly and withstands SAW-induced stress.
Implementation Method 1
The step of forming the coating layer forms the coating layer on a front surface of the piezoelectric element substrate, an end surface of the piezoelectric element substrate, and a corner portion between the front surface of the piezoelectric element substrate and the end surface of the piezoelectric element substrate
Implementation Method 2
a piezoelectric element substrate with an IDT (Interdigital Transducer) comprising a comb-like electrode pair is used to generate a surface acoustic wave (SAW) and thus atomize liquid
Data Source
AI summary
A surface acoustic wave module (SAW module) includes a piezoelectric element substrate including a piezoelectric body, an IDT disposed on a front surface of the piezoelectric element substrate and including a comb-like electrode pair, and a coating layer covering the piezoelectric element substrate and the IDT. The coating layer is disposed on the front surface of the piezoelectric element substrate, an end surface of the piezoelectric element substrate, and a corner portion between the front surface of the piezoelectric element substrate and the end surface of the piezoelectric element substrate.