Piezoelectric Micromachined Ultrasonic Transducer Package Structure
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Solution Overview
Problem
The thickness of the welding part in piezoelectric micromachined ultrasonic transducers limits design flexibility in electronic devices, and the lack of a flat surface for attachment hampers assembly due to traditional pad openings.
Innovation Solution
A package structure featuring a silicon substrate with through holes and protective layers, a piezoelectric composite film with electrode layers, and metal layers that allow for a flat surface attachment by transferring the pad to the backside, reducing overall thickness through silicon perforation technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If traditional pad opening structure is used, then welding connection is achieved, but overall thickness cannot be reduced and flat surface for attachment is lost
Solution Approach 1:
The pad structure is inverted from the traditional top-opening configuration to a bottom-side configuration. The first pad is formed on the bottom surface of the silicon substrate, while the second pad is formed on the side surface of the encapsulation structure. This inversion allows the top surface to remain flat for attachment while maintaining welding connectivity through the enclosed cavity structure.
Solution Approach 2:
The pad structure is nested within the enclosed cavity formed by the encapsulation structure. The first pad is embedded in the bottom surface of the silicon substrate, and the second pad is integrated into the side surface of the encapsulation structure. This nesting approach hides the pad openings from the top surface, enabling a flat attachment surface while preserving electrical connectivity.
2Adaptability or versatility
If traditional welding part structure is used, then electrical connection is established, but design flexibility is limited due to thickness constraints
Solution Approach 1:
The electrical connection path is extended from a single-dimensional vertical structure to a multi-dimensional configuration. The first metal layer and second metal layer are formed in different spatial dimensions, with the first metal layer on the bottom surface and the second metal layer on the side surface. This dimensional change allows for reduced thickness while maintaining connectivity.
Solution Approach 2:
The welding connection is segmented into multiple components distributed across different surfaces. Instead of a single thick welding part, the connection is divided into the first pad on the bottom surface, the first metal layer, the second metal layer, and the second pad on the side surface. This segmentation reduces the thickness requirement while preserving electrical connectivity.
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
Enables a flat surface attachment to electronic devices, reducing the overall thickness of the transducer and enhancing design flexibility in electronic device assembly.
Implementation Method 1
a piezoelectric composite film, which is on the first protective layer. A vertical projection of the piezoelectric composite film at least partially overlaps with the groove
Data Source
AI summary
A package structure of a piezoelectric micromachined ultrasonic transducer includes a silicon substrate, a first protective layer, a piezoelectric composite film, a first metal layer, a second metal layer, a first pad, a second pad and a second protective layer. The silicon substrate is provided with a first through hole and a second through hole. The first protective layer is provided with a groove, a first communication hole and a second communication hole. The piezoelectric composite film includes a first electrode layer and a second electrode layer respectively filling the first communication hole and the first through hole, and the second communication hole and the second through hole so as to be connected to the first metal layer and the second metal layer. A surface of the second protective layer away from the piezoelectric composite film is a flat surface.