MEMS Substrate Warping Prevention via Adhesive Bump Overlap
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Solution Overview
Problem
In MEMS devices, such as inkjet recording heads, the adhesive layer placement between substrates can lead to warping, unstable electrical connections, and adverse effects on piezoelectric element vibration properties due to its proximity to the bumps or low bonding strength, affecting the reliability of electrode connections.
Innovation Solution
The adhesive layer is positioned in close proximity to the bumps, overlapping with them to prevent warping and enhance bonding strength, while using a photosensitive resin for precise shaping and avoiding contact with piezoelectric elements to maintain their displacement integrity, and the bumps include an elastic core with a metal film for reliable connection even under substrate deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the adhesive layer is arranged far from the bump, then the bonding strength is sufficient, but the substrates may warp
Solution Approach 1:
The adhesive layer is positioned selectively at specific locations (overlapping with bumps or in recessed portions) rather than uniformly distributed, providing local reinforcement exactly where needed to prevent warping while maintaining sufficient bonding strength
2Stability of the object's composition
If the adhesive layer is arranged in close proximity to the bump, then substrate warping is prevented, but the adhesive layer may spread to the drive region of piezoelectric elements and adversely affect vibration properties
Solution Approach 1:
The adhesive layer is confined to specific regions (overlapping with bumps or within recessed portions) that are spatially separated from the piezoelectric element drive regions, providing warping prevention locally without interfering with the vibration properties of the piezoelectric elements
Solution Approach 2:
The bump structure serves as an intermediary element between the adhesive layer and the piezoelectric elements, allowing the adhesive to be positioned close to the bump for warping prevention while the bump itself acts as a barrier preventing adhesive spread to the piezoelectric element drive region
3Quantity of substance
If thin-film piezoelectric elements are used for high density mounting, then mounting density is improved, but electrical connection to driver circuit becomes difficult
Solution Approach 1:
Bumps are introduced as intermediary connection elements between the thin-film piezoelectric elements and the driver circuit substrate, providing robust electrical connection points that bridge the gap between high-density element mounting and reliable electrical connectivity
Solution Approach 2:
The connection architecture transitions from planar two-dimensional connections to three-dimensional structures with bumps extending vertically, adding a height dimension that enables reliable electrical connection while maintaining high horizontal density of piezoelectric elements
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 ensures reliable and stable connections between primary and secondary electrodes, inhibits substrate warping, and maintains the displacement integrity of piezoelectric elements, enhancing the overall performance and durability of MEMS devices.
Implementation Method 1
piezoelectric elements provided on one surface side of the passage-forming substrate... drives the piezoelectric elements with the driver circuit, thereby generates pressure changes in liquid contained in the pressure generating chambers
Implementation Method 2
the bumps include an elastic core with a metal film for reliable connection even under substrate deformation
Data Source
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AI summary
Provided are an MEMS device, a head, and a liquid jet device in which substrates are inhibited from warping, so that a primary electrode and a secondary electrode can be reliably connected to each other. Included are a primary substrate 30 provided with a bump 32 including a primary electrode 34, and a secondary substrate 10 provided with a secondary electrode 91 on a bottom surface of a recessed portion 36 formed by an adhesive layer 35. The primary substrate 10 and the secondary substrate 30 are joined together with the adhesive layer 35, the primary electrode 34 is electrically connected to the secondary electrode 91 with the bump 32 inserted into the recessed portion 36, and part of the bump 32 and the adhesive layer 35 forming the recessed portion 36 overlap each other in a direction in which the bump 32 is inserted into the recessed portion 36.