SAW Package Structure With Pillar Electrodes for Low-Height Mounting
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Solution Overview
Problem
Current surface acoustic wave devices face challenges in reducing size and height while maintaining mounting strength, particularly due to issues with solder bumps leading to potential breaks in connecting portions.
Innovation Solution
The design incorporates a piezoelectric substrate with an IDT electrode, a support layer, a cover layer, and a pillar-shaped electrode where the support and cover layers do not cover the exposed portions of the pillar-shaped electrode, allowing for reduced size and height, and enabling mounting through both the top and side surfaces for improved strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a WLP structure with pillar-shaped electrode and solder bump is used, then the size and height of surface acoustic wave device are decreased, but breaks may occur in connecting portions between solder bump and electrode
Solution Approach 1:
The invention transitions from single-point solder bump connection to multi-surface exposed portion connection. The pillar-shaped electrode's exposed portions extend in multiple directions (top surface and side surfaces), enabling the joining member to connect at multiple locations and orientations, thereby distributing mechanical stress and improving mounting reliability while maintaining compact size.
Solution Approach 2:
The connection interface is segmented into multiple exposed portions of the pillar-shaped electrode rather than a single solder bump. This segmentation allows the joining member to make contact with multiple discrete locations on the pillar-shaped electrode, distributing the mounting load and reducing the risk of breaks in any single connecting portion.
2Reliability
If solder bump is provided on pillar-shaped electrode, then electrical connection is achieved, but height of device increases
Solution Approach 1:
The invention merges the electrical connection function and mechanical mounting function into a single integrated structure. The pillar-shaped electrode itself serves as both the electrical conductor and the mounting interface through its exposed portions, eliminating the need for separate solder bumps and reducing overall device height.
3Reliability
If support layer and cover layer completely cover pillar-shaped electrode, then protection is provided, but size and height cannot be further decreased
Solution Approach 1:
The support layer and cover layer are configured to provide protection only where necessary, leaving specific exposed portions of the pillar-shaped electrode uncovered. This local differentiation allows the electrode to be protected in most areas while maintaining exposed connection surfaces for mounting, achieving a balance between protection and size reduction.
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 decreases the size and height of the surface acoustic wave device, enhances mounting strength by allowing dual-surface connection, and reduces the risk of tombstone effects during mounting, while also improving heat dissipation and versatility in material selection.
Implementation Method 1
an IDT electrode provided on one main surface of a piezoelectric substrate produces a surface acoustic wave
Data Source
AI summary
A surface acoustic wave device includes a piezoelectric substrate, an IDT electrode, a support layer, a cover layer, and a pillar-shaped electrode. The IDT electrode is provided on a main surface of the piezoelectric substrate. The support layer is disposed around a region where the IDT electrode is provided and has a larger height from the main surfaces than a height of the IDT electrode therefrom. The cover layer is disposed on the support layer and covers the IDT electrode. The pillar-shaped electrode is located on one of the main surfaces where the pillar-shaped electrode is in contact with the support layer. The pillar-shaped electrode is electrically connected to the IDT electrode. The pillar-shaped electrode includes a top surface and a side surface. Each of the top surface and the side surface includes a portion exposed to outside.