Wafer-Level Multi-Layer PZT Microactuator Manufacturing
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Solution Overview
Problem
The manufacturing of small piezoelectric microactuators requires more efficient processes, as existing methods necessitate multiple processing steps at the device level, increasing complexity and cost.
Innovation Solution
A method for manufacturing multi-layer piezoelectric microactuators with inactive constraining layers entirely or almost entirely at the wafer level, using aligned wafers with through-holes for electrical vias and metallization layers, allowing for poling and singulation before individual device assembly, thus reducing the need for additional device-level processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple processing steps are performed at the device level, then manufacturing precision can be maintained, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent segments the manufacturing process into wafer-level batch processing and device-level final assembly. Multiple PZT layers are processed together as a wafer stack through stacking, bonding, and dicing operations, enabling parallel fabrication of multiple devices while maintaining precision through controlled segmentation of the overall manufacturing flow
Solution Approach 2:
The patent transitions from traditional device-level processing to wafer-level processing by adding a new dimension of fabrication scale. Entire PZT wafers are stacked and processed together in the thickness dimension, allowing batch manufacturing of multi-layer structures before singulation into individual devices, thereby reducing process complexity
2Productivity
If wafer-level processing is used, then productivity increases, but manufacturing precision may be compromised
Solution Approach 1:
Alignment holes are formed in the PZT wafers before stacking, and alignment features are prepared in advance. This preliminary alignment preparation ensures that when wafers are stacked and bonded, precise registration between layers is achieved through pre-established mechanical interlocks and alignment references, maintaining manufacturing precision during high-productivity wafer-level processing
Solution Approach 2:
The patent uses alignment holes and alignment features as intermediary elements that facilitate precise registration between stacked wafers. These intermediary structures enable accurate positioning during the bonding process, ensuring that subsequent dicing and device separation maintain the required precision despite the batch processing approach
3Length of moving object
If inactive constraining layers are added to increase effective stroke length, then actuator performance improves, but device complexity increases
Solution Approach 1:
The patent merges the structural function of inactive constraining layers with the active PZT layers into a unified multi-layer wafer structure. By stacking alternating active and inactive layers during wafer-level processing, the device achieves increased effective stroke length through the combined mechanical compliance of the layered structure, while the fabrication complexity is managed through batch processing of the entire stack
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 approach enhances manufacturing efficiency by completing the multi-layer PZT devices with active and inactive layers at the wafer level, increasing the effective stroke length and simplifying the assembly process, while reducing the number of necessary steps and costs.
Implementation Method 1
Piezoelectric microactuators, sometimes simply called PZTs for short
Implementation Method 2
A first metallization layer is formed on the first wafer, and a patterned second metallization layer is formed on the second wafer
Data Source
AI summary
A multi-level piezoelectric actuator is manufactured using wafer level processing. Two PZT wafers are formed and separately metallized for electrodes. The metallization on the second wafer is patterned, and holes that will become electrical vias are formed in the second wafer. The wafers are then stacked and sintered, then the devices are poled as a group and then singulated to form nearly complete individual PZT actuators. Conductive epoxy is added into the holes at the product placement step in order to both adhere the actuator within its environment and to complete the electrical via thus completing the device. Alternatively: the first wafer is metallized; then the second wafer having holes therethrough but no metallization is stacked and sintered to the first wafer; and patterned metallization is applied to the second wafer to both form electrodes and to complete the vias. The devices are then poled as a group, and singulated.