Liquid Discharging Head Dual Adhesive Bonding
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Solution Overview
Problem
Existing liquid discharging heads face issues with improper sealing at the lower portions of lead terminals due to cavities and air bubbles, and corrosion caused by adhesives contacting the lead terminals during bonding, leading to faulty connections and reduced bond strength.
Innovation Solution
A liquid discharging head is designed using two types of adhesives: a photo-curable adhesive with high bond strength for bonding the electric wiring substrate to the supporting member, and a thermosetting adhesive with higher volume resistivity applied closer to the lead terminals to prevent electrical connection and corrosion, ensuring firm bonding while minimizing adhesive contact with the lead terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a photo-curable adhesive with high bond strength is used to bond the electric wiring substrate to the supporting member, then the bond strength is improved, but the lead terminals may be corroded by the adhesive
Solution Approach 1:
The bonding process is segmented into two distinct adhesive applications: a first adhesive applied to the entire bonding surface for strong bonding, and a second adhesive with higher volume resistivity applied near the lead terminals to prevent corrosion. This segmentation allows each adhesive to perform its specific function without interfering with the other.
Solution Approach 2:
Different regions of the bonding interface are assigned different adhesive properties: the region away from lead terminals uses a photo-curable adhesive with high bond strength, while the region near lead terminals uses an adhesive with higher volume resistivity to prevent electrical conduction and corrosion. This local differentiation optimizes both bonding strength and corrosion protection.
2Object-affected harmful factors
If a thermosetting adhesive with higher volume resistivity is used to prevent corrosion of lead terminals, then the corrosion resistance is improved, but the bond strength is reduced
Solution Approach 1:
The bonding process is segmented into two distinct adhesive applications: a first adhesive applied to the entire bonding surface for strong bonding, and a second adhesive with higher volume resistivity applied near the lead terminals to prevent corrosion. This segmentation allows each adhesive to perform its specific function without interfering with the other.
Solution Approach 2:
Different regions of the bonding interface are assigned different adhesive properties: the region away from lead terminals uses a photo-curable adhesive with high bond strength, while the region near lead terminals uses an adhesive with higher volume resistivity to prevent electrical conduction and corrosion. This local differentiation optimizes both bonding strength and corrosion protection.
3Strength
If the adhesive is applied to a greater thickness to ensure firm bonding, then the bond strength is improved, but the adhesive may protrude and contact the lead terminals
Solution Approach 1:
The first adhesive is applied to the entire bonding surface first to establish strong bonding, then the second adhesive with higher volume resistivity is applied near the lead terminals as a protective layer. This preliminary action ensures that the bonding function is established before the protective function is added.
Solution Approach 2:
The second adhesive acts as an intermediary barrier between the first adhesive and the lead terminals. It prevents the conductive first adhesive from contacting the lead terminals while allowing the bonding function to be maintained through the first adhesive's broader application area.
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
The solution effectively prevents corrosion of lead terminals and ensures strong bonding between the electric wiring substrate and the supporting member, reducing the risk of faulty connections and improving the sealing process by using a combination of adhesives with different properties.
Implementation Method 1
a photo-curable adhesive whose principal component is epoxy resin and that is electrically conductive is used
Data Source
AI summary
A liquid discharging head includes a recording element substrate configured to discharge a liquid; an electric wiring substrate that is provided with a lead terminal that is connected to the recording element substrate; and a supporting member to which the electric wiring substrate is bonded. The electric wiring substrate is bonded to the supporting member with two or more types of adhesives including at least a first adhesive and a second adhesive whose volume resistivity is higher than that of the first adhesive, a bond strength of the first adhesive is higher than a bond strength of the second adhesive, and, at the supporting member, the second adhesive is applied such that the second adhesive is provided closer to the lead terminal than the first adhesive.