Elastic Wave Filter Bump Layout for Transmit-Receive Heat Isolation

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Solution Overview

Problem

Elastic wave devices face issues with heat propagation from transmit filters to receive filters due to higher thermal conductivity of support substrates compared to piezoelectric materials, leading to overheating and potential troubles in receive filters.

Innovation Solution

The implementation of a sealing resin layer and strategically designed bumps on the mount board to cover both filters, with specific height and joint area relations, and IDT electrode positions to enhance heat dissipation and prevent heat propagation from the transmit filter to the receive filter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the support substrate has high thermal conductivity to dissipate heat from the transmit filter, then heat dissipation from the transmit filter is improved, but heat propagates to the receive filter causing overheating

Engineering Contradiction:

Improveheat dissipation from transmit filterVSAvoidtemperature of receive filter

Core Design Contradiction:

Loss of energyVSTemperature

Solution Approach 1:

The support substrate is divided into a first region beneath the transmit filter with high thermal conductivity for heat dissipation, and a second region beneath the receive filter with low thermal conductivity to block heat propagation. This segmentation allows different thermal conductivity requirements in different areas of the same substrate.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the support substrate are assigned different thermal conductivity properties: the first region has high thermal conductivity to efficiently dissipate heat from the transmit filter, while the second region has low thermal conductivity to prevent heat from reaching the receive filter. This local differentiation resolves the contradiction between heat dissipation and heat isolation.

Inventive Principle:

Principle #3Local quality

2Reliability

If an insulating material is used to cover the filters, then electrical insulation is improved, but heat propagation from transmit filter to receive filter occurs

Engineering Contradiction:

Improveelectrical insulation between filtersVSAvoidheat propagation to receive filter

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The support substrate provides localized thermal management: the first region offers high thermal conductivity for heat dissipation under the transmit filter, while the second region offers low thermal conductivity to block heat propagation to the receive filter. This local differentiation allows the insulating material to maintain electrical insulation without causing harmful heat propagation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The support substrate acts as an intermediary between the transmit and receive filters, with its dual-region thermal conductivity design mediating the thermal interaction. The low thermal conductivity second region specifically prevents heat from the transmit filter from reaching the receive filter, while the high thermal conductivity first region ensures proper heat dissipation where needed.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 improves heat dissipation from the transmit filter, reducing or preventing heat propagation to the receive filter, thereby minimizing overheating issues and maintaining filter performance.

Implementation Method 1

The first bump and the second bump satisfy at least one of a first relation A1>A2 and B1>B2, and a second relation H1<H2... improve dissipation of heat generated due to heating of a transmit filter

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

The sealing resin layer is disposed on the mount board so as to cover the transmit filter and the receive filter... reducing or preventing propagation of heat from the transmit filter to a receive filter

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 3

a piezoelectric material layer is disposed on the support substrate, and an interdigital transducer (IDT) electrode is disposed on the piezoelectric material layer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS10637433B2Elastic wave device, radio-frequency front-end circuit, and communication device

Publication Date: 2020.04.28 MURATA MFG CO LTD

AI summary

An elastic wave device includes a mount board, a transmit filter, a receive filter, and a sealing resin layer. The transmit filter includes a first piezoelectric substrate, and is joined to the mount board by first bumps. The receive filter includes a second piezoelectric substrate, and is joined to the mount board by second bumps. The sealing resin layer is provided on the mount board. The height of each first bump is H1; the joint area, on the first piezoelectric substrate side, of each first bump is A1; and the joint area, on the mount board side, of each first bump is B1; the height of each second bump is H2; the joint area, on the second piezoelectric substrate side, of each second bump is A2; and the joint area, on the mount board side, of each second bump is B2. The first bumps and the second bumps satisfy at least one of: A1>A2 and B1>B2; and H1<H2.