Piezoelectric Element Cable Connection via Resin Film Solder Control
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Solution Overview
Problem
The challenge in producing high-density inkjet heads for OLED displays is the occurrence of short-circuits between piezoelectric elements due to excess solder when connecting flexible cables with fine pitches, which reduces production yields.
Innovation Solution
A method involving a thermosetting resin film sandwiched between piezoelectric element electrodes and substrate electrodes, where the resin is softened and cured, then used to direct and solidify solder, preventing excess solder from causing short-circuits by creating a controlled path for excess solder to follow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If substrate electrodes are connected to piezoelectric elements with fine pitch, then pixel resolution is improved, but short-circuit between adjacent piezoelectric elements occurs due to excess solder
Solution Approach 1:
A resin film is introduced as an intermediary substance between the substrate electrodes and piezoelectric elements. The resin film fills the gaps between adjacent electrodes and solidifies to form isolation structures that prevent excess solder from causing short-circuits, while allowing the fine pitch connection to be maintained for high pixel resolution
Solution Approach 2:
The resin film is applied in advance before the soldering process. By pre-positioning the resin film between the electrodes, the patent prepares the isolation structures beforehand, ensuring that when solder is applied, excess solder cannot bridge adjacent electrodes even with fine pitch spacing
2Reliability
If holes or recesses are formed on insulating substrate to collect excess solder, then short-circuit is prevented, but device complexity increases
Solution Approach 1:
The patent extracts the solder collection function from the substrate structure itself and transfers it to the resin film. Instead of forming holes or recesses in the insulating substrate, the resin film is applied on the substrate surface and serves as the isolation medium, simplifying the substrate structure while maintaining short-circuit prevention
Solution Approach 2:
The resin film acts as an intermediary layer that provides the solder isolation function without requiring modifications to the substrate structure. This mediator approach avoids the complexity of forming holes or recesses in the substrate while achieving the same reliability goal
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 approach effectively prevents short-circuits between adjacent piezoelectric elements, enhancing the reliability and yield of inkjet head production by ensuring precise soldering even without recesses or holes between substrate electrodes, thus improving the connection of flexible cables with fine wiring pitches.
Implementation Method 1
a resin film made of a thermosetting resin is sandwiched between the element electrode and the substrate electrode
Implementation Method 2
the resin is softened and cured, then used to direct and solidify solder
Implementation Method 3
melting the solder, and pushing out along the line a portion of the solder located at an opposing position
Implementation Method 4
solidifying the solder between the plurality of substrate electrodes and the plurality of element electrodes
Implementation Method 5
The inkjet head includes a piezoelectric element that applies pressure to ink
Data Source
AI summary
A connection method includes softening a resin film of a thermosetting resin by heating an element electrode of a piezoelectric body and a substrate electrode of a flexible cable to be connected to the piezoelectric body with the element electrode and the substrate electrode being pressed into contact with each other via the resin film; partially pushing out the molten resin film from an opposing position of the element electrode and the substrate electrode so as to bring a solder layer provided on the substrate electrode into contact with the element electrode; curing the resin film and melting solder in the solder layer by further raising a heating temperature; discharging excess solder in a direction defined by the cured resin film; and then solidifying the solder in the solder layer so as to solder the element electrode and the substrate electrode together.