Segmented Flex Circuit Bumps Reduce Piezo Actuator Cross-Talk
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Solution Overview
Problem
In piezoelectric inkjet print heads, the mechanical coupling between flexible printed circuits and piezoelectric transducers causes cross-talk, limiting the density of actuators due to unintended movement and electrical shorts, especially as actuator density increases.
Innovation Solution
A flexible printed circuit with bumps and reliefs is used, where the reliefs reduce the stiffness between bumps to minimize movement transfer, thereby reducing cross-talk and maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bumped flexible printed circuits are used to eliminate conductive epoxy, then electrical shorting is prevented, but mechanical coupling causes cross-talk between adjacent actuators
Solution Approach 1:
The flexible printed circuit is segmented into individual isolated bumps rather than a continuous conductive layer. Each bump is electrically and mechanically isolated from adjacent bumps, preventing cross-talk while maintaining reliable electrical connection to its corresponding actuator. The bumps are separated by non-conductive spaces in the flexible circuit substrate.
Solution Approach 2:
The flexible printed circuit has different mechanical properties at different locations: the bumps have high local stiffness for reliable electrical contact, while the spaces between bumps have low stiffness to isolate mechanical coupling. This local variation in mechanical properties allows each bump to independently contact its actuator without transmitting movement to adjacent bumps.
2Manufacturing precision
If actuator density is increased to improve printing resolution, then printing quality improves, but cross-talk increases due to mechanical coupling
Solution Approach 1:
By segmenting the flexible circuit into discrete isolated bumps, the mechanical coupling between adjacent actuators is eliminated. This allows actuators to be placed closer together without cross-talk, enabling higher actuator density and improved printing resolution.
Solution Approach 2:
The non-conductive spaces between bumps act as mechanical intermediaries that decouple adjacent actuators. These spaces allow the flexible circuit to flex locally at each bump position without transmitting mechanical movement to adjacent bumps, enabling higher actuator density.
3Object-affected harmful factors
If the flexible printed circuit has low modulus to reduce movement, then cross-talk is reduced, but structural integrity is compromised
Solution Approach 1:
The flexible printed circuit exhibits different mechanical properties at different locations: the bumps have high local stiffness (high modulus) to maintain structural integrity and provide reliable electrical contact, while the spaces between bumps have low stiffness to reduce movement transfer. This local differentiation resolves the contradiction between strength and cross-talk reduction.
Solution Approach 2:
Segmenting the flexible circuit into discrete bumps with non-conductive spaces between them allows each bump to maintain high structural integrity independently. The segmentation prevents the need for uniformly low modulus throughout the entire circuit, as each bump can be structurally robust while the spaces between provide mechanical isolation.
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
The solution effectively reduces cross-talk between adjacent actuators, allowing for higher actuator density in print heads without electrical shorts, enhancing printing resolution and reliability.
Implementation Method 1
When a current is supplied to a piezoelectric transducer, typically through electrical connection with an electrode, the piezoelectric transducer bends or deflects.
Implementation Method 2
Conductive epoxy (e.g., silver epoxy) is then stenciled or otherwise inserted into the aperture. An electrically conductive metallization, often referred to as a flexible printed circuit, is then positioned over the adhesive and epoxy layer.
Data Source
AI summary
An actuator assembly including a flexible printed circuit and a method for making such an actuator assembly are provided. The flexible printed circuit includes a body having a top side and a bottom side, with the body defining a plurality of bumps extending from the bottom side. A first bump of the plurality of bumps is disposed adjacent to a second bump of the plurality of bumps, and the body further defines at least one relief configured to reduce movement of the second bump caused by movement of the first bump. The flexible printed circuit also includes a plurality of contact pads disposed on the bottom side of the body at least partially at the plurality of bumps, with the plurality of contacts pads being configured to be electrically coupled to a power source and to a piezoelectric transducer.