Flex Circuit Interconnect for Ink Jet Print Heads Using Dielectric Underfill
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Solution Overview
Problem
Conventional methods for manufacturing high-density piezoelectric ink jet print heads face challenges such as high material costs due to the use of expensive conductive materials, complex processing, and increased risk of electrical shorts, particularly as transducer arrays become more dense, requiring simplified and cost-effective connection methods for piezoelectric elements.
Innovation Solution
The method involves attaching a piezoelectric element array to a diaphragm, electrically coupling conductive flexible printed circuit electrodes, and using a dielectric underfill to encapsulate the elements, eliminating the need for a conventional interstitial layer and standoff layer, which simplifies the manufacturing process and reduces material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional interstitial layer and standoff layer methods are used for electrical interconnection, then reliable electrical connections can be achieved, but material costs increase and manufacturing complexity increases
Solution Approach 1:
The patent removes the interstitial layer and standoff layer from the manufacturing process, extracting only the essential function of electrical connection. The flex circuit is directly bonded to the piezoelectric element tops using conductive adhesive, eliminating unnecessary intermediate layers while maintaining connection reliability.
Solution Approach 2:
The patent combines the electrical connection function and mechanical support function into a single direct bonding step. The flex circuit serves both as the electrical interconnect and as the structural support, merging multiple functions that were previously separated into distinct layers and steps.
2Manufacturing precision
If transducer array density is increased to improve printing resolution, then printing resolution improves, but available area for electrical interconnects decreases
Solution Approach 1:
The patent transitions from planar electrical interconnection to three-dimensional bonding. The flex circuit is bonded directly to the tops of the piezoelectric elements, utilizing the vertical dimension to achieve connections without consuming lateral space, thereby enabling higher transducer density.
Solution Approach 2:
The patent uses a flexible printed circuit as the interconnect medium. The flex circuit's flexibility allows it to conform to the elevated tops of the piezoelectric elements, enabling direct bonding in a high-density arrangement without requiring additional lateral space for routing.
3Adaptability or versatility
If more ports are added to pass through diaphragm for each jet chamber, then ink flow pathways are provided for each jet, but manufacturing complexity increases
Solution Approach 1:
The patent makes the diaphragm multi-functional by having it serve both as the flexible membrane for jet actuation and as the ink distribution manifold. The diaphragm includes integrated ink flow pathways that deliver ink to each jet chamber, eliminating the need for separate ports and internal manifolds.
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 simplifies the manufacturing of high-density ink jet print heads by reducing material costs, minimizing electrical shorts, and enabling easier scaling with increased transducer density, while maintaining reliable electrical connections.
Implementation Method 1
a dielectric underfill between the flexible printed circuit and the diaphragm
Implementation Method 2
When a voltage is applied to a piezoelectric element, typically through electrical connection with an electrode electrically coupled to a voltage source, the piezoelectric element bends or deflects
Data Source
AI summary
A method for forming an ink jet print head can include attaching a plurality of piezoelectric elements to a diaphragm of a jet stack subassembly, electrically attaching a flex circuit to the plurality of piezoelectric elements, then dispensing an dielectric underfill between the flex circuit and the jet stack subassembly. The use of an underfill after attachment of the flex circuit eliminates the need for the patterned removal of an interstitial material from the tops of the piezoelectric elements, and removes the requirement for a patterned standoff layer. In an embodiment, electrical contact between the flex circuit and the piezoelectric elements is established through physical contact between bump electrodes of the flex circuit and the piezoelectric elements, without the use of a separate conductor, thereby eliminating the possibility of electrical shorts caused by misapplication of a conductor.