Piezoelectric Speaker Fabrication via BEOL Solder Bump Assembly
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Solution Overview
Problem
Conventional piezoelectric speakers are fabricated using MEMS technologies, resulting in complex and costly fabrication processes.
Innovation Solution
A method for forming a piezoelectric speaker involving a piezoelectric actuator with a piezoelectric layer, bottom and top electrodes, and a speaker frame with a bump structure, where the bottom electrode is combined with the speaker frame through a solder layer, and the process employs BEOL processes to reduce fabrication costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If MEMS technologies are used to fabricate piezoelectric speakers, then the fabrication precision and device performance are improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The fabrication process is divided into two independent segments: (1) forming the piezoelectric actuator on a first substrate using standard thin-film deposition techniques, and (2) forming the speaker frame on a second substrate separately. These segments are later assembled together through bump structures, allowing each to be optimized independently while reducing overall process complexity
Solution Approach 2:
The piezoelectric actuator and speaker frame are prepared in advance on separate substrates with pre-formed structures (electrodes, bump structures, solder layers) before final assembly. This preliminary preparation allows for standardized manufacturing of components that can be readily combined, reducing the complexity of the overall fabrication process
2Manufacturing precision
If MEMS technologies are used to fabricate piezoelectric speakers, then the manufacturing precision is improved, but the manufacturing cost increases
Solution Approach 1:
The piezoelectric actuator structure serves multiple functions: it acts as both the electro-acoustic transducer element and the upper speaker frame component. The speaker frame structure similarly serves as both the mechanical housing and the electrical connection substrate. This multi-functionality reduces the number of separate components and assembly steps required, thereby reducing manufacturing cost
Solution Approach 2:
The bump structures and solder layers are formed through self-aligned processes where the positioning is determined by the underlying substrate patterns and component geometries. This self-alignment eliminates the need for complex external alignment equipment and procedures, reducing manufacturing cost while maintaining precision
3Reliability
If the piezoelectric actuator is combined with the speaker frame through solder layer and bump structure, then the electrical connection reliability is improved, but the manufacturing process complexity increases
Solution Approach 1:
Bump structures serve as intermediary mechanical and electrical connectors between the piezoelectric actuator and speaker frame, while the solder layer acts as an intermediary bonding material. These intermediaries provide reliable electrical connections while accommodating thermal expansion differences and mechanical stress, enhancing overall connection reliability
Solution Approach 2:
The mechanical support function and electrical connection function are merged into the same bump structure and solder layer assembly. This integration eliminates the need for separate mechanical fasteners and electrical connectors, reducing assembly complexity while maintaining reliable electrical connections
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 method simplifies the fabrication process and reduces costs while maintaining the functionality of piezoelectric speakers by using a BEOL process-based approach.
Implementation Method 1
a piezoelectric material is used as an electro-acoustic transducer element. A sound output mechanism of the piezoelectric speaker is that, an application of an AC voltage to two surface of the piezoelectric element causes a generation of shape distortion of the piezoelectric element, so that a metal diaphragm is vibrated, thereby generating a sound
Implementation Method 2
forming a solder layer on a top surface of the bump structure; and combining the bottom electrode of the piezoelectric actuator with the speaker frame through the solder layer
Data Source
AI summary
A piezoelectric speaker and a method for forming the piezoelectric speaker are provided. The method includes: providing a piezoelectric actuator which includes a piezoelectric layer, a bottom electrode and a top electrode, wherein the bottom electrode and the top electrode are on two opposite surfaces of the piezoelectric layer; providing a speaker frame which includes a base and a bump structure on the base; forming a solder layer on a top surface of the bump structure; and combining the bottom electrode of the piezoelectric actuator with the speaker frame through the solder layer.