MEMS Interconnect Groove for Adhesive Isolation
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Solution Overview
Problem
In MEMS devices, particularly liquid ejecting heads, there is a challenge in maintaining a secure electrical connection between the driving circuit and interconnect pattern due to adhesive interference, which can lead to incorrect driving of piezoelectric actuators and increased device size.
Innovation Solution
A MEMS device configuration where the interconnect pattern has a connection portion extending between the bonding region and an opening, with a groove formed between the connection region and border, and a branching portion to prevent adhesive overflow, ensuring a secure electrical connection and reducing the device's size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sealing substrate is bonded to the protective substrate while avoiding the interconnect pattern, then the electrical connection is secure, but the device size increases in the planar direction
Solution Approach 1:
The invention merges the bonding region with the interconnect pattern by allowing the sealing substrate to bond to a region that includes part of the interconnect pattern. The groove structure integrates both functions: it serves as an adhesive barrier to protect the bonding interface while simultaneously defining the bonding region boundary. This merging eliminates the need for a separate avoidance region, reducing the overall device footprint while maintaining electrical connection reliability.
Solution Approach 2:
The interconnect pattern is segmented into different functional regions: a bonding region where the sealing substrate bonds to the protective substrate, and a non-bonding region where electrical connections are made. The groove structure further segments the bonding region from the non-bonding region, creating clear spatial separation between adhesive application areas and electrical connection areas. This segmentation allows the sealing substrate to bond to part of the interconnect pattern without compromising electrical connections.
2Area of stationary object
If the sealing substrate overlaps with the interconnect pattern to reduce bonding region size, then the device size is reduced, but adhesive may enter the interconnect pattern and damage electrical connections
Solution Approach 1:
The groove is formed in advance during the interconnect pattern fabrication process, creating a pre-defined barrier structure before adhesive application. This preliminary action ensures that when adhesive is applied to bond the sealing substrate, it cannot penetrate into the electrical connection regions. The groove acts as a pre-established protective feature that prevents harmful adhesive intrusion while allowing the sealing substrate to overlap with and bond to part of the interconnect pattern.
Solution Approach 2:
The groove structure serves as an intermediary barrier between the adhesive and the electrical connection regions. It is positioned at the boundary of the bonding region, acting as a physical mediator that allows adhesive to be contained within the bonding region while preventing its intrusion into the electrical connection areas. This intermediary structure enables the sealing substrate to bond to the interconnect pattern without direct adhesive contact with electrical connections.
3Reliability
If a groove is formed in the connection portion to prevent adhesive entry, then electrical connection reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The groove structure is merged with the interconnect pattern fabrication process, combining two functions into a single integrated feature. The groove serves dual purposes: it acts as an adhesive barrier to protect electrical connections and simultaneously defines the bonding region boundary. By merging these functions into a single structural element formed during standard fabrication, the manufacturing complexity is minimized while achieving reliable electrical connections.
Solution Approach 2:
The groove dimensions and depth are optimized as fabrication parameters to achieve the desired adhesive barrier function without requiring additional manufacturing steps. By adjusting parameters such as groove width, depth, and position during the interconnect pattern formation process, the adhesive blocking capability is enhanced while maintaining compatibility with existing fabrication capabilities. This parameter optimization allows the groove to effectively prevent adhesive entry without significantly increasing manufacturing complexity.
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 effectively suppresses adhesive interference with the electrical connection, ensuring reliable operation of the pressure generating unit and miniaturization of the MEMS device by reducing the bonding region size.
Implementation Method 1
piezoelectric actuators provided on one surface side of the flow channel formation substrate
Implementation Method 2
a sealing substrate that includes an opening and that is bonded to the protective substrate using an adhesive
Data Source
AI summary
A MEMS device includes a protective substrate on which is mounted a driving circuit that drives a piezoelectric actuator and on which is formed an interconnect pattern electrically connected to the driving circuit, and a sealing substrate that includes a first opening and that is bonded to the protective substrate using an adhesive so that part of the interconnect pattern is located between the protective substrate and the sealing substrate. The interconnect pattern includes a connection portion that extends from a bonding region where the protective substrate and the sealing substrate are bonded by the adhesive to the first opening, and that has a connection region electrically connected to the driving circuit. A groove is formed in the connection portion between the connection region and a border between the bonding region and the connection portion.