Acoustic Wave Resonator Double Protective Layer Adhesion
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Solution Overview
Problem
Conventional bulk acoustic wave filters face issues with delamination and short-circuit defects due to weak adhesion of protective layers, and damage from external pressure, particularly in the manufacturing process of solder reflow and molding operations.
Innovation Solution
A double protective layer structure is implemented, where the internal protective layer is formed of insulating materials like silicon dioxide, aluminum oxide, or silicon nitride with strong adhesion, directly in contact with the substrate, and the external protective layer is made of a polymer material with better elastic properties, exposed to the outside environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single protective layer is used, then the structure is simple, but adhesion is weak causing delamination and short-circuit defects
Solution Approach 1:
The protective layer is divided into multiple layers: an internal protective layer in contact with the substrate and an external protective layer covering the internal layer. This segmentation allows each layer to perform its specific function - the internal layer provides strong adhesion to prevent delamination, while the external layer provides additional protection, thereby resolving the contradiction between structural simplicity and adhesion reliability.
Solution Approach 2:
The patent uses composite material structure where the internal protective layer and external protective layer are made of different materials with complementary properties. The internal layer is designed for strong adhesion to the substrate, while the external layer provides enhanced protection. This composite approach enables the system to achieve both structural simplicity and high adhesion strength simultaneously.
2Reliability
If a protective layer with strong adhesion is used, then delamination is prevented, but elastic properties are insufficient to withstand external pressure
Solution Approach 1:
The protective layer is segmented into an internal protective layer and an external protective layer, where each layer is optimized for different properties. The internal layer is designed with strong adhesion to prevent delamination, while the external layer is designed with superior elastic properties to withstand external pressure during solder reflow and molding operations. This segmentation resolves the contradiction by assigning different functional requirements to different layers.
Solution Approach 2:
Different regions of the protective layer structure are given different material qualities - the internal layer near the substrate has strong adhesion characteristics, while the external layer exposed to the environment has enhanced elastic properties. This local quality differentiation allows the system to simultaneously achieve strong adhesion and pressure resistance without compromising either property.
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 configuration effectively prevents delamination and short-circuit defects during solder reflow and withstands external pressure, enhancing the reliability and durability of the acoustic wave resonator.
Implementation Method 1
an internal protective layer directly in contact with the second surface of the substrate and formed of an insulating material including an adhesion that is stronger than an adhesion of other layers
Implementation Method 2
an external protective layer disposed on an outer surface of the internal protective layer and being externally exposed, wherein the external protective layer is formed of an insulating material including an elastic properties that is stronger than an elastic properties of the internal protective layer
Implementation Method 3
induces resonance using piezoelectric characteristics of a piezoelectric dielectric material deposited on a silicon wafer
Data Source
AI summary
An acoustic wave resonator includes: a substrate; a resonating portion formed on a first surface of the substrate; a metal pad connected to the resonating portion through a via hole formed in the substrate; and a protective layer disposed on a second surface of the substrate and including a plurality of layers, wherein the plurality of layers includes an internal protective layer directly in contact with the second surface of the substrate and formed of an insulating material including an adhesion that is stronger than an adhesion of other layers, among the plurality of layers.