Printhead Assembly PCB Isolation from Corrosive Ink
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Solution Overview
Problem
The challenge of creating a strong structure with robust electrical connections for tiny printhead die slivers is compounded by the need to protect printed circuit boards from corrosive inks and printing fluids, which existing technologies fail to adequately address.
Innovation Solution
A printhead assembly is developed with a molded structure that includes multiple printhead die slivers and a printed circuit board affixed to the back, where bond wires connect each die sliver to conductors, and a discrete flow structure with passages carries printing fluid, sealed with adhesive to isolate the PCB from both the fluid supply and dispensing fluids, ensuring the PCB's integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a printed circuit board is integrated into the molded printhead assembly to strengthen structure and electrical connections, then structural strength and electrical connection robustness are improved, but the PCB becomes vulnerable to corrosive effects of inks and printing fluids
Solution Approach 1:
The printhead assembly is divided into distinct functional zones: a fluid handling region (molding with channels and die slivers) and an electrical region (PCB with conductors). This segmentation allows the PCB to provide structural and electrical support without direct exposure to corrosive fluids, as the fluid channels are contained within the molding material that separates the two regions.
Solution Approach 2:
The molding material acts as an intermediary barrier between the PCB and the printing fluids. The molding encapsulates the PCB while containing the fluid channels, preventing direct contact between the corrosive fluids and the PCB. This intermediary structure allows the PCB to be integrated for strength and electrical connections without suffering from fluid exposure.
2Reliability
If protective coatings are applied to protect the PCB from corrosive fluids, then the PCB's durability is improved, but the device complexity and manufacturing steps increase
Solution Approach 1:
The harmful function of the molding material is extracted and repurposed: instead of merely encapsulating the PCB, the molding is designed to simultaneously contain fluid channels and provide corrosion protection. This eliminates the need for separate protective coatings on the PCB, as the molding's primary fluid containment function also serves as a protective barrier.
Solution Approach 2:
The molding material performs multiple functions: it contains the printing fluids in channels, protects the PCB from fluid exposure, provides structural support, and enables electrical connections through the die slivers. This multi-functionality eliminates the need for separate protective coatings, reducing device complexity while maintaining PCB durability.
3Manufacturing precision
If the printhead die size is reduced to create tiny die slivers, then the precision and density of ejection chambers are improved, but the structural strength and electrical connection robustness deteriorate
Solution Approach 1:
Multiple tiny die slivers are merged into a single molded assembly that is integrated with a robust PCB. The individual die slivers, which would be too small to provide structural strength on their own, are combined within a unified molding structure that is attached to the PCB. This merging allows the tiny dies to achieve high precision while the combined assembly maintains structural integrity and robust electrical connections through the PCB.
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 solution effectively isolates the printed circuit board from corrosive fluids, maintaining structural and electrical integrity, eliminating the need for protective coatings and allowing for thinner moldings and varied printhead die configurations, while promoting robust electrical connections.
Implementation Method 1
The flow structure is affixed to the molding with an adhesive that seals off the printed circuit board from the passages in the flow structure and from the channels in the molding
Implementation Method 2
Bond wires electrical connect each die sliver to conductors in the printed circuit board
Data Source
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AI summary
In one example, a printhead assembly includes a molding with multiple printhead dies exposed at a front part of the molding and channels in a back part of the molding to carry printing fluid to the dies. The printhead assembly also includes a printed circuit board affixed to the back part of the molding, not covering any of the channels, and an electrical connection between each die and the printed circuit board.