MEMS Device Sealing via Segmented Substrate Spaces
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Solution Overview
Problem
MEMS devices, such as ink jet recording heads and SAW oscillators, face challenges in electrically connecting high-density piezoelectric elements to drive circuits while maintaining moisture protection, as traditional sealing methods can lead to increased pressure and positional deviations due to thermal expansion, and atmosphere-open through-holes compromise the integrity of the sealing mechanism.
Innovation Solution
A MEMS device configuration involving a first and second substrate with a third electrode for electrical connection, a piezoelectric element, and an adhesive to create a closed space, along with a through-hole in one of the substrates to communicate with the atmosphere, allowing for heat-curing of the adhesive and reducing pressure and positional deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If through-holes are provided to open sealed spaces to the atmosphere to prevent pressure increase, then pressure inside sealed spaces is controlled, but liquid or gas may enter and moisture protection becomes insufficient
Solution Approach 1:
The space between substrates is divided into two distinct regions: a sealed space containing functional elements (piezoelectric elements, electrodes) that requires moisture protection, and an atmosphere-open space that communicates with the external environment through through-holes. This spatial segmentation allows differential pressure control while maintaining protection for sensitive components.
Solution Approach 2:
Different regions of the substrate assembly are assigned different sealing properties: the sealed space surrounding functional elements maintains hermetic sealing for moisture protection, while the atmosphere-open space allows pressure equalization. This local differentiation of sealing quality resolves the contradiction between pressure control and moisture protection.
2Strength
If adhesive is heated to high temperature to cure the adhesive, then bonding strength is improved, but gas inside sealed spaces expands and positional deviation occurs
Solution Approach 1:
The bonding structure is segmented into sealed regions (containing functional elements) and atmosphere-open regions (with through-holes). During high-temperature adhesive curing, the atmosphere-open spaces allow gas expansion and pressure equalization, preventing excessive pressure buildup that would cause positional deviation, while the sealed regions maintain their protective function.
Solution Approach 2:
The atmosphere-open through-holes are formed in advance before adhesive curing. This preliminary action ensures that when high-temperature curing is performed, the gas expansion pathway is already available, preventing pressure-induced positional deviation during the bonding process.
3Productivity
If piezoelectric elements are disposed at high density, then device functionality is improved, but electrical connection to drive circuits becomes difficult
Solution Approach 1:
The electrical connection structure (third electrode) is extracted and positioned in the atmosphere-open space, separate from the densely packed piezoelectric elements. This extraction allows simplified wiring and connection to drive circuits while maintaining high-density arrangement of functional elements in the sealed space.
Solution Approach 2:
The electrical connection approach moves from planar connections within the sealed space to three-dimensional routing through the atmosphere-open space. This dimensional transition provides additional routing pathways for electrical connections, simplifying the connection structure despite high-density element arrangement.
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 enhances the reliability of MEMS devices by stabilizing electrical connections and preventing moisture degradation, while maintaining the structural integrity of the device by isolating sensitive components from atmospheric influences.
Implementation Method 1
an adhesive which adheres the first substrate and the second substrate to each other
Implementation Method 2
a piezoelectric element which is disposed between the first substrate and the second substrate
Data Source
AI summary
A MEMS device which includes an adhesive which adheres a first substrate and a second substrate to each other, in which a first space which includes an electrode, an individual electrode, a common electrode, a bump electrode, and a piezoelectric element and which is configured as a closed space which is isolated from an atmosphere by the first substrate, the second substrate, and the adhesive is disposed in a space between the first substrate and the second substrate, and in which a second space which does not include any of the electrode, the individual electrode, the common electrode, the bump electrode, or the piezoelectric element and which communicates with the atmosphere due to a through-hole which penetrates at least one of the first substrate and the second substrate is disposed in the space between the first substrate and the second substrate.