SAW Package Support Layout to Prevent Cover Layer Wrinkles

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Solution Overview

Problem

Surface acoustic wave devices with wafer level package (WLP) structures face challenges in mold resistance and lamination properties due to wrinkles and thickness issues when resin cover layers are attached, leading to reduced reliability.

Innovation Solution

The use of vertically arranged partition-support layers with a specific configuration, including first and second partition-support layers that extend in parallel directions, reduces the likelihood of wrinkles and maintains uniform thickness, enhancing mold resistance and lamination properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a partition-support layer with a crank shape extending in both longitudinal and lateral directions is provided, then reinforcement strength and mold resistance are improved, but wrinkles are generated in the cover layer and lamination property deteriorates

Engineering Contradiction:

Improvemold resistanceVSAvoidlamination property

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The partition-support layer is divided into multiple straight-line segments arranged in parallel rather than a single continuous crank shape. This segmentation eliminates the curved portions that cause cover layer wrinkles while maintaining the partitioning function for reinforcement.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of using a crank shape that extends in both directions (which causes wrinkles), the invention inverts the approach by using straight-line segments that extend only in the longitudinal direction. This inversion of the geometric configuration resolves the lamination issue while preserving mold resistance.

Inventive Principle:

Principle #13The other way round (Inversion)

2Strength

If the partition-support layer extends in both longitudinal and lateral directions to partition the hollow space, then reinforcement strength is enhanced, but the cover layer is crushed and manufacturing precision is reduced

Engineering Contradiction:

Improvereinforcement strengthVSAvoidcover layer thickness uniformity

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The partition-support structure is segmented into multiple straight-line segments positioned parallel to each other. This segmentation removes the lateral extension components that cause cover layer crushing, allowing uniform thickness while maintaining reinforcement through the distributed straight segments.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The partition-support layers provide sufficient reinforcement strength through their arrangement and material properties without excessively extending in the lateral direction. This partial action approach achieves the needed reinforcement while avoiding the harmful effects of lateral extension on cover layer integrity.

Inventive Principle:

Principle #16Partial or excessive action

3Stress or pressure

If a crank-shaped partition-support layer is used to improve mold resistance, then pressure resistance is enhanced, but wrinkles are generated and reliability is reduced

Engineering Contradiction:

Improvepressure resistanceVSAvoiddevice reliability

Core Design Contradiction:

Stress or pressureVSReliability

Solution Approach 1:

The partition-support function is achieved through multiple straight-line segments rather than a continuous crank shape. This segmentation maintains the pressure resistance needed for mold resistance while eliminating the wrinkle-generation mechanism, thereby improving overall device reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention converts the potentially harmful crank shape into beneficial straight-line segments. By removing the curved portions that cause wrinkles, the straight segments provide clean, wrinkle-free support that maintains pressure resistance while improving reliability through better lamination properties.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 improves the mold resistance, lamination property, and reliability of surface acoustic wave devices by minimizing wrinkles and maintaining uniform thickness during resin attachment, while also increasing the electrode-design area.

Implementation Method 1

interdigital transducer (IDT) electrodes are provided on a piezoelectric substrate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS11476831B2Surface acoustic wave device

Publication Date: 2022.10.18 MURATA MFG CO LTD

AI summary

A surface acoustic wave device includes a piezoelectric substrate, an interdigital transducer electrode that is disposed on a main surface of the piezoelectric substrate, a plurality of partition-support layers each of which is arranged in a region of the main surface surrounded by an outer periphery of the main surface, and a cover layer that is disposed above the plurality of partition-support layers and that covers the interdigital transducer electrode. The plurality of partition-support layers include a first partition-support layer and a second partition-support layer that are adjacent to each other, and a portion of the first partition-support layer and a portion of the second partition-support layer do not overlap each other when viewed from a second direction perpendicular or substantially perpendicular to a first direction in which the plurality of partition-support layers extend.