SAW Filter Terminal Routing Layout for Low-Coupling Flip-Chip Mounting
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Solution Overview
Problem
Flip-chip mounting of surface acoustic wave devices leads to degradation of electrical characteristics, such as reduced attenuation and isolation, due to increased coupling capacity between input and output terminals, which is not suitable for downsizing wireless device filters.
Innovation Solution
A surface acoustic wave device with a comb-shaped electrode pattern and a grounding pattern between input and output terminals, connected through bumps, reduces coupling capacity and maintains filter performance by using a routing pattern to separate terminals without expanding the device's footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If flip-chip mounting is used to downsize the device, then the device footprint is reduced, but the coupling capacity between input and output terminals increases causing degradation of electrical characteristics
Solution Approach 1:
A grounding electrode is introduced as an intermediary element positioned between the input and output terminals. This grounding electrode acts as a mediator to reduce the coupling capacity between the input and output terminals, thereby preventing degradation of electrical characteristics while maintaining the compact flip-chip mounting structure.
Solution Approach 2:
The electrode terminals are arranged in a specific spatial configuration where the input and output terminals are positioned on opposite sides with the grounding electrode interspersed between them. This dimensional arrangement in the electrode pattern creates effective separation and reduces coupling capacity without increasing the overall device footprint.
2Reliability
If terminal spacing is increased to reduce coupling capacity, then electrical characteristics are maintained, but the device footprint expands
Solution Approach 1:
The grounding electrode is merged with the existing electrode structure between the input and output terminals. By combining the grounding function with the existing electrode pattern, the solution reduces coupling capacity without requiring additional space or separate components, thus maintaining compact device dimensions.
3Reliability
If bonding wires are used to connect terminals, then electrical characteristics can be maintained with proper spacing, but the device requires larger spatial spacing and cannot be downsized
Solution Approach 1:
The mechanical bonding wire connection system is replaced with a direct flip-chip mounting method using bumps for electrical connection. This substitution eliminates the need for bonding wires and the associated spatial spacing requirements, enabling device downsizing while maintaining electrical characteristics through the grounding electrode configuration.
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 achieves low insertion loss and high attenuation characteristics, ensuring the device meets standard values for wireless filters even when flip-chip-mounted, thereby preventing device enlargement and maintaining effective filter performance.
Implementation Method 1
an IDT pattern as described in Japanese Patent Application Laid-Open Publication No. 2004-194269 as an example and shown in FIG. 1 is formed on a piezoelectric element (piezoelectric substrate) not shown such as LiTaO3, LiNbO3, Li2B4O7 or crystal
Implementation Method 2
a combination of multiple (double) -mode SAW filters (DMS) having a plurality of (two) resonance modes by utilizing a plurality of (two) standing waves generated between reflecting electrodes
Data Source
AI summary
A surface acoustic wave device having a surface acoustic wave filter having a comb-shaped electrode pattern formed on a piezoelectric element, electrode terminals for inputting and outputting of the surface acoustic wave filter are connected with corresponding electrode patterns of a package through bumps, wherein the comb-shaped electrode pattern has a pair of reflective electrodes, and an input comb-shaped electrode and an output comb-shaped electrode disposed between the pair of reflective electrodes; and an electrode terminal of either the input comb-shaped electrode or an output comb-shaped electrode is disposed such that the electrode terminal is positioned on the side opposite to the side of the other electrode terminal sandwiching a grounded electrode using a routing pattern.