Ladder Filter Thermal Path Through Busbar and Terminal Structure
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Solution Overview
Problem
Ladder filters in wireless communication devices lack sufficient thermal dissipation, which degrades their electric power handling capability due to the absence of a thermal dissipation path from the elastic wave resonator.
Innovation Solution
Incorporating a thermally conductive member with higher thermal conductivity than the interlayer insulating film, in contact with at least one of the signal or ground terminals, and an interlayer insulating film on busbars within the ladder filter to enhance thermal dissipation, while maintaining electrical conductivity and miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional ladder filter configuration is used, then the device structure is simple, but thermal dissipation is insufficient leading to degraded electric power handling capability
Solution Approach 1:
The busbar is divided into multiple segments with different configurations: some busbars have interlayer insulating films disposed on them while others do not. This segmentation allows different portions of the filter to have different thermal dissipation characteristics, enabling optimized thermal management without completely redesigning the entire structure.
Solution Approach 2:
A thermally conductive member with higher thermal conductivity than the interlayer insulating film is introduced as an intermediary thermal path. This member is disposed on the interlayer insulating film and contacts signal or ground terminals, creating an enhanced thermal dissipation pathway that bridges the resonator and heat sink without disrupting the electrical function.
2Volume of moving object
If the filter size is reduced for miniaturization, then the device becomes more compact, but thermal dissipation capability may be compromised
Solution Approach 1:
The thermal dissipation path is extended into the vertical dimension by disposing the thermally conductive member on the interlayer insulating film and establishing thermal contact with terminals above the resonator plane. This three-dimensional thermal pathway enables effective heat dissipation in a compact footprint without requiring larger surface area.
Solution Approach 2:
The structure combines materials with different thermal conductivities in a composite arrangement: the interlayer insulating film provides electrical isolation while the thermally conductive member provides enhanced thermal conduction. This composite approach allows simultaneous achievement of electrical function and improved thermal dissipation in miniaturized form.
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 temperature increases by about 5% and enhances thermal dissipation, improving the electric power handling capability and miniaturization of the ladder filter while maintaining attenuation characteristics.
Implementation Method 1
a thermally conductive member made of a material possessing thermal conductivity higher than that of the interlayer insulating film and disposed on the interlayer insulating film. The thermally conductive member is in contact with at least one of the first signal terminal, the second signal terminal, and the ground terminal
Implementation Method 2
A ladder filter according to a preferred embodiment of the present invention includes a piezoelectric substrate, a first signal terminal, a second signal terminal, and a ground terminal disposed on the piezoelectric substrate
Implementation Method 3
The plurality of IDT electrodes define a plurality of elastic wave resonators with a predetermined pass band
Data Source
AI summary
A ladder filter includes a piezoelectric substrate, an antenna terminal, a transmission terminal, and ground terminals on the piezoelectric substrate, and IDT electrodes. Each of the IDT electrodes is disposed on the piezoelectric substrate and includes a plurality of electrode fingers and a pair of busbars to which first ends of the plurality of electrode fingers are connected commonly. The IDT electrodes define elastic wave resonators. The ladder filter further includes an interlayer insulating film disposed on at least one of the busbars and a thermally conductive member made of a material with thermal conductivity higher than that of the interlayer insulating film and disposed on the interlayer insulating film. The thermally conductive member is in contact with at least one of the antenna terminal, the transmission terminal, and the ground terminals.