Elastic Wave Duplexer Sealing Member Dielectric Constant
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Solution Overview
Problem
Conventional elastic wave duplexers experience degradation in isolation characteristics due to direct reaching waves caused by capacitance between input and output terminals, which is attributed to the sealing resin used in surface acoustic wave devices.
Innovation Solution
An elastic wave duplexer design featuring a sealing member with a lower dielectric-constant portion facing the transmission and reception elastic wave filter elements, reducing capacitance and direct reaching waves, thereby enhancing isolation characteristics. The sealing member includes a base portion made of a first dielectric material and a lower dielectric-constant portion made of a second material with a lower dielectric constant, arranged to face the filter elements on the side opposite the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing resin is used to seal off the surface acoustic wave element, then the element is protected against environmental stresses, but capacitance is generated between input and output terminals causing direct reaching waves that degrade isolation characteristics
Solution Approach 1:
The sealing member is designed with different dielectric constants in different regions: a first dielectric material with higher dielectric constant in regions not facing the filter elements, and a second dielectric material with lower dielectric constant in regions facing the transmission and reception filter elements. This local differentiation reduces capacitance in critical areas while maintaining sealing protection, thereby reducing direct reaching waves without compromising environmental protection.
Solution Approach 2:
The sealing member is constructed as a composite structure combining two different dielectric materials. The first dielectric material provides general sealing and structural support, while the second dielectric material with lower dielectric constant is strategically placed to minimize capacitance effects. This composite approach allows the sealing member to simultaneously provide environmental protection and reduce harmful capacitance-induced direct reaching waves.
2Ease of manufacture
If a uniform sealing material is used, then manufacturing is simplified, but capacitance between terminals cannot be minimized effectively
Solution Approach 1:
Rather than using a uniform sealing material, the invention applies different dielectric materials in specific regions of the sealing member. The second dielectric material with lower dielectric constant is placed specifically in regions facing the filter elements where capacitance reduction is most critical, while the first dielectric material is used in other regions. This localized differentiation targets the capacitance problem without requiring complete redesign of the entire sealing structure.
Solution Approach 2:
The invention changes the dielectric constant parameter of the sealing material in specific regions. By using a second dielectric material with a lower dielectric constant in regions facing the filter elements, the capacitance between terminals is reduced. This parameter change is strategically applied only where needed to minimize capacitance effects while maintaining the overall sealing function.
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 design effectively reduces direct reaching waves and improves isolation between transmission and reception terminals by minimizing capacitance, resulting in a higher degree of isolation and improved signal integrity.
Implementation Method 1
a lower dielectric-constant portion made of a second dielectric material having a lower dielectric constant than the first dielectric constant and located in a region of the sealing member that faces the transmission elastic wave filter element on a side opposite from the substrate with respect to the transmission elastic wave filter element
Data Source
AI summary
A transmission elastic wave filter element and a reception elastic wave filter element each flip-chip mounted to a principal surface of a substrate are sealed off by a sealing member. The sealing member includes a base portion in contact with the principal surface of the substrate and made of a first dielectric material, and a lower dielectric-constant portion made of a second dielectric material having a dielectric constant lower than that of the first dielectric material and arranged in at least one of a region of the sealing member that faces the transmission elastic wave filter element on a side opposite from the substrate with respect to the transmission elastic wave filter element, and a region of the sealing member that faces the reception elastic wave filter element on the side opposite from the substrate with respect to the reception elastic wave filter element.