Standoff Layer Supports for Piezoelectric Inkjet Interconnects
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Solution Overview
Problem
High-density piezoelectric ink jet print heads face challenges in achieving reliable electrical connections and interconnects due to reduced surface area for bonding at higher resolutions, leading to weaker connections that may fail under thermal cycling and actuation stresses.
Innovation Solution
The use of standoff layer supports within the interstitial spaces between piezoelectric elements, which are physically attached to a standoff layer with openings exposing the upper surface of each element, allows for a larger bonding area and more secure attachment of a circuit layer, increasing the effective bond area by over 120% and providing a robust physical connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the density of piezoelectric elements is increased to improve printing resolution, then the jet density is improved, but the surface area available for electrical interconnect bonding is reduced
Solution Approach 1:
The patent introduces a standoff layer that extends vertically from the substrate, creating a third dimension for electrical interconnection. This allows the bonding surface to extend upward in the Z-direction rather than being constrained to the XY-plane, effectively increasing bonding area without increasing the footprint on the substrate. The standoff layer acts as a vertical extension that provides additional surface area for conductive material deposition and electrical connection.
Solution Approach 2:
The patent embeds conductive material within the standoff layer structure itself, nesting the electrical interconnect functionality within the bonding structure. The standoff layer contains embedded conductive traces or particles that provide both mechanical support and electrical connection pathways, allowing multiple functions to be integrated within a compact vertical structure.
2Productivity
If the surface area for bonding is reduced due to higher density piezoelectric elements, then the jet density is improved, but the reliability of electrical interconnects deteriorates
Solution Approach 1:
By extending the bonding interface vertically through the standoff layer, the patent creates additional bonding surface area that is not constrained by the reduced horizontal spacing between high-density piezoelectric elements. This vertical extension provides redundant bonding area that can accommodate thermal expansion, contraction, and mechanical stress without compromising connection integrity.
Solution Approach 2:
The standoff layer appears to be constructed from composite materials that combine structural support functionality with electrical conductivity. This composite structure provides both mechanical strength to support the bonding process and electrical pathways for signal transmission, thereby improving reliability through material composition rather than just geometric expansion.
3Productivity
If the dimensions of piezoelectric elements are reduced to increase density, then the jet density is improved, but the bond area for surrounding adhesive is reduced
Solution Approach 1:
The standoff layer provides a vertical platform that extends the available bonding area upward, allowing adhesive to be applied on the top surface of the standoff layer rather than only on the substrate plane. This vertical extension compensates for the reduced horizontal space available around smaller, higher-density piezoelectric elements.
Solution Approach 2:
The standoff layer acts as an intermediary structure between the substrate and the piezoelectric elements, providing an additional bonding interface. This intermediate platform allows adhesive to bond to the standoff layer rather than directly to the substrate, effectively creating an additional bonding zone that compensates for reduced available area due to higher element density.
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 results in a more reliable and robust electrical interconnect between the piezoelectric elements and the circuit layer, reducing stress and improving the reliability of the connection, especially at higher print head resolutions.
Implementation Method 1
When a voltage is applied to a piezoelectric element, typically through electrical connection with an electrode electrically coupled to a power source, the piezoelectric element bends or deflects
Implementation Method 2
a quantity (e.g., a microdrop) of conductor such as conductive epoxy, conductive paste, or another conductive material is dispensed individually on the top of each piezoelectric element. Electrodes of the flex circuit or PCB are placed in contact with each microdrop to facilitate electrical communication
Data Source
AI summary
An ink jet print head including a plurality of standoff layer supports in an interstitial region between adjacent piezoelectric elements, and method of formation. The plurality of standoff layer supports can be formed from the same layer(s) as the piezoelectric elements, or from a dielectric layer such as a polymer. The standoff layer supports increase an area to which a standoff layer can be attached, thereby forming a more secure attachment of a circuit layer such as a flex circuit or a printed circuit board to a jet stack subassembly.