Adhesive Wetting Control in Stacked Substrate Bonding
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Solution Overview
Problem
The miniaturization of electronic devices, such as liquid ejecting heads, is hindered by the wetting and spreading of adhesives, which can disrupt the bonding process and lead to bonding failures and short circuits, especially in densely packed drive regions with piezoelectric elements.
Innovation Solution
The use of a spacer and a structure body with a curved surface on the second substrate, where the adhesive is applied to the structure body and extends to the adhesion region, regulating the wetting and spreading of the adhesive and preventing it from reaching the drive region, while using a non-conductive adhesive to prevent short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is applied to bond substrates, then bonding strength is improved, but adhesive spreads widely on substrate disrupting miniaturization
Solution Approach 1:
The adhesive application region is locally restricted to the peripheral region of the substrate, away from the drive region. This local quality approach ensures that adhesive provides bonding strength where needed (at the periphery) without spreading into the drive region, thus enabling miniaturization while maintaining bonding integrity.
2Strength
If adhesive is applied to bond substrates, then bonding strength is improved, but short circuits and bonding failures occur in drive region
Solution Approach 1:
The substrate surface is segmented into distinct functional regions: a drive region for piezoelectric elements and a peripheral region for adhesive application. This segmentation prevents adhesive from reaching the drive region, eliminating short circuits and bonding failures while maintaining adequate bonding strength in the peripheral region.
Solution Approach 2:
The peripheral region acts as an intermediary zone that accommodates the adhesive, preventing direct contact between adhesive and the sensitive drive region. This intermediary space ensures that bonding strength is achieved without compromising the electrical integrity of the piezoelectric elements.
3Stability of the object's composition
If substrates are bonded with adhesive, then structural integrity is improved, but adhesive wetting and spreading disrupts bonding process
Solution Approach 1:
The substrate design preliminarily defines a peripheral region designated for adhesive application, before the actual bonding process. This preliminary spatial arrangement controls adhesive wetting and spreading by providing a predetermined safe zone, ensuring manufacturing precision and structural integrity without adhesive intrusion into the drive region.
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 wetting and spreading, enabling miniaturization and densification of electronic devices by maintaining the integrity of the drive region and preventing bonding failures and short circuits, while also blocking outgassing effects.
Implementation Method 1
a first substrate (131) including a structure body (40) protruded from one surface; and a second substrate (33) stacked and disposed facing the one surface through a spacer (43), in which the first substrate (131) and the spacer (43) are bonded to each other by an adhesive (49)
Data Source
AI summary
An electronic device includes a first substrate including a structure body protruded from one surface; and a second substrate stacked and disposed facing the one surface through a spacer, in which the first substrate and the spacer are bonded to each other by an adhesive, and in which the adhesive is extended up to the structure body along the one surface.