Surface Mount BAW Device Connections
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Solution Overview
Problem
Conventional Wafer-Level-Packaged (WLP) Bulk Acoustic Wave (BAW) devices face challenges in reducing device size while maintaining effective external electrical connections, leading to space constraints and increased costs due to the size and placement of copper pillar connections.
Innovation Solution
The WLP BAW device incorporates a surface mount connection structure with a copper or gold connection layer and a tin or tin-lead layer, positioned adjacent to the WLP enclosure with a reduced distance, allowing for a smaller opening in the piezoelectric layer and reducing the need for additional space, along with a surface mount connection extension that covers a portion of the cap to enhance cap strength and reduce delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper pillar connections are used for external electrical connection, then reliable electrical connection is achieved, but device size increases due to space requirements and round shape occupying significant area
Solution Approach 1:
The patent transitions from a three-dimensional copper pillar connection extending vertically to a two-dimensional surface mount connection structure that lies substantially in the plane of the piezoelectric layer. This dimensional change allows the connection to be made adjacent to the WLP enclosure without requiring significant vertical space, thereby reducing the overall device footprint while maintaining electrical connectivity.
Solution Approach 2:
Instead of extending the connection structure vertically outward from the piezoelectric layer as in conventional copper pillar designs, the patent inverts the approach by placing the connection structure in the plane of the layer and extending it horizontally adjacent to the enclosure. This inversion of the connection geometry eliminates the need for additional vertical space and reduces the area occupied by the connection structure.
2Reliability
If opening in piezoelectric layer is positioned far from WLP enclosure to accommodate copper pillar, then electrical connection is maintained, but device size increases
Solution Approach 1:
The patent repositions the opening and connection structure from a vertical arrangement (where the copper pillar extends outward from the layer) to a horizontal arrangement (where the connection structure lies in the plane of the layer adjacent to the enclosure). This dimensional change allows the opening to be positioned much closer to the WLP enclosure, reducing the distance parameter while maintaining electrical connectivity.
3Area of stationary object
If surface mount connection structure is positioned adjacent to WLP enclosure, then device size is reduced, but heat dissipation and structural integrity challenges arise
Solution Approach 1:
The patent introduces a surface mount connection structure that serves as an intermediary between the piezoelectric layer and the external environment. This connection structure is positioned adjacent to the WLP enclosure and provides a pathway for heat dissipation while maintaining structural integrity. The connection structure acts as a mediator that resolves the conflict between compact positioning and thermal management.
4Reliability
If conventional copper pillar connection is used, then electrical connection is achieved, but manufacturing cost increases due to processing constraints and space requirements
Solution Approach 1:
The patent changes the connection structure from a vertical copper pillar to a horizontal surface mount structure lying in the plane of the piezoelectric layer. This dimensional change simplifies the manufacturing process by eliminating the need for complex vertical alignment and bonding processes associated with copper pillars, thereby reducing manufacturing costs while maintaining 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
This design effectively reduces the device size, improves heat dissipation, and enhances the structural integrity of the WLP enclosure by eliminating space constraints between the enclosure and the connection structure, while maintaining reliable electrical connections.
Implementation Method 1
The surface mount connection structure covers a first portion of a top surface of the cap and extends continuously over a side portion of the WLP enclosure and to the exposed portion of the bottom electrode lead through the opening of the piezoelectric layer
Implementation Method 2
The transducer 18 includes a piezoelectric layer 20, which is sandwiched between a top electrode 22 and a bottom electrode 24
Implementation Method 3
The reflector 16 is typically formed by a stack of reflector layers (not shown), which alternate in material composition to produce a significant reflection coefficient at the junction of adjacent reflector layers
Data Source
AI summary
The present disclosure relates to a Wafer-Level-Packaged (WLP) Bulk Acoustic Wave (BAW) device that includes a BAW resonator, a WLP enclosure, and a surface mount connection structure. The BAW resonator includes a piezoelectric layer with an opening and a bottom electrode lead underneath the piezoelectric layer, such that a portion of the bottom electrode lead is exposed through the opening of the piezoelectric layer. The WLP enclosure includes a cap and an outer wall that extends from the cap toward the piezoelectric layer to form a cavity. The opening of the piezoelectric layer is outside the cavity. The surface mount connection structure covers a portion of a top surface of the cap and extends continuously over a side portion of the WLP enclosure and to the exposed portion of the bottom electrode lead through the opening of the piezoelectric layer.