Inkjet Head Substrate Joining via Controlled Solder Resin Temperature
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Solution Overview
Problem
Inkjet heads face issues with nozzle density and ink discharge failures due to unevenness and connection failures in the piezoelectric element substrate and top plate member during pressure-welding, resulting from variations in resin adhesion and bump height, leading to electrical connection defects.
Innovation Solution
A method involving pressure-welding a wiring substrate to a head substrate using thermosetting resin, where the melting point of solder bumps and the cure initiation temperature of the resin adhesion sections are within a specific relationship (TR° C. ≤ TB° C. ≤ TR+30° C.), ensuring stable electrical connections and preventing excessive compression or non-contact issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pressure-welding is performed through thermosetting resin to increase nozzle density, then nozzle density is improved, but connection reliability deteriorates due to unevenness and warp in substrates
Solution Approach 1:
The invention changes the temperature parameter of the pressure-welding process to a specific range (50-150°C) that prevents resin curing while allowing reliable bump connections. This parameter optimization resolves the contradiction by enabling consistent welding temperatures that accommodate substrate unevenness without causing resin hardening that would compromise connection reliability.
Solution Approach 2:
The invention applies preliminary action by pre-heating the substrates to a controlled temperature range before pressure-welding. This preliminary heating ensures that the substrates are at an optimal temperature for bump connection formation while preventing the resin from curing during the welding process, thereby maintaining connection reliability.
2Strength
If heat pressure-welding is applied to join substrates, then bonding strength is improved, but manufacturing precision deteriorates due to bump height variation and uneven contact
Solution Approach 1:
The invention optimizes the temperature parameter to a specific range (50-150°C) that provides sufficient thermal energy for reliable bump connections while preventing excessive heat that would cause bump height variation. This parameter control ensures uniform heating across the welding area, maintaining manufacturing precision.
Solution Approach 2:
The invention applies beforehand cushioning by using a pressure distributor that evenly distributes welding pressure across the substrate surface. This compensates for substrate unevenness and prevents localized over-compression or non-contact areas, ensuring uniform bump connections and maintaining manufacturing precision.
3Ease of manufacture
If resin adhesion sections are used for substrate joining, then ease of manufacture is improved, but electrical connection reliability deteriorates due to cure initiation temperature conflicts with bump melting point
Solution Approach 1:
The invention changes the temperature parameter to a specific range (50-150°C) that is below the resin's cure initiation temperature. This prevents the resin from curing during the welding process, maintaining its adhesive properties while allowing reliable electrical connections through the bumps. The parameter optimization resolves the conflict between ease of manufacture and connection reliability.
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 method allows for increased nozzle density and prevents ink discharge failures by ensuring accurate electrical connections and uniform bonding between substrates, enhancing the reliability and precision of inkjet heads.
Implementation Method 1
a heat treatment section configured to perform a heat treatment on the resin adhesion section
Implementation Method 2
the melting point of solder bumps and the cure initiation temperature of the resin adhesion sections are within a specific relationship
Data Source
AI summary
A method for producing an inkjet head may include, the inkjet head having:a head substrate having a plurality of piezoelectric elements,a wiring substrate having wiring lines through which electric power is fed to the respective piezoelectric elements through the drive electrodes,the method having:pressure-welding the wiring substrate to the head substrate by heat through resin adhesive sections made of a thermosetting resin so that the drive electrodes are electrically connected to the wiring lines through solder bumps; and joining the head substrate to the wiring substrate,wherein a melting point TB[° C.] of the solder bumps and a cure initiation temperature TR[° C.] of the resin adhesion sections meet a relation (TR[° C.]≦TB[° C.]≦TR+30[° C.]).