Plasma Polymerized Layer for Flexible Circuit Corrosion Protection
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Solution Overview
Problem
Flexible circuits in micro-fluid ejection devices face corrosion issues due to the brittleness of existing covercoat materials, which can lead to delamination and electrical shorts, and current protective measures like gold coatings are costly and inefficient.
Innovation Solution
A plasma polymerized layer is deposited on the conductive layers of flexible circuits using monomers such as fluorocarbons, hydrocarbons, and silicon-containing compounds to enhance corrosion resistance and adhesion, eliminating the need for a separate covercoat and gold coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If epoxy or acrylate covercoat material is applied to protect conductive layers, then corrosion protection is provided, but the material is brittle and develops cracks during manufacturing
Solution Approach 1:
The patent changes the material parameters by replacing brittle epoxy or acrylate covercoat materials with a polymeric material that has improved flexibility and adhesion properties. This material parameter change eliminates crack formation during manufacturing while maintaining corrosion protection capabilities.
Solution Approach 2:
The patent uses a composite structure where a polymeric material is applied over the conductive layers. This polymeric material combines flexibility, adhesion, and corrosion resistance in a single integrated layer, eliminating the need for separate covercoat and adhesive layers.
2Reliability
If gold coating is applied to lead beams to reduce corrosion, then corrosion resistance is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive gold coating with a cost-effective polymeric material that provides comparable corrosion protection. This substitution significantly reduces material costs while maintaining the required corrosion resistance performance for the lead beams.
Solution Approach 2:
The patent changes the protective material from precious metal (gold) to a synthetic polymeric material, altering the material composition parameter to achieve the same functional outcome (corrosion protection) at a lower cost.
3Reliability
If encapsulant material is used to protect semiconductor substrate, then corrosion protection is provided, but ink migration under the encapsulant causes delamination and electrical shorts
Solution Approach 1:
The patent applies the polymeric material to the flexible circuit and lead beams before final assembly and encapsulation. This preliminary protective coating prevents ink migration and corrosion at critical interfaces before the encapsulant is applied, eliminating the root cause of delamination and electrical shorts.
Solution Approach 2:
The polymeric material serves as an intermediary protective layer between the conductive elements and the corrosive ink environment. It acts as a barrier that prevents ink contact with metal surfaces, thereby preventing corrosion and maintaining adhesion stability throughout the device lifecycle.
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 plasma polymerized layer significantly reduces corrosion, promotes adhesion between the flexible circuit and encapsulant material, and provides a cost-effective solution by integrating corrosion protection and adhesion promotion in a single step, enhancing the longevity and reliability of micro-fluid ejection devices.
Implementation Method 1
A plasma polymerized layer is deposited on at least a portion of the conductive layer to reduce corrosion of the conductive layer
Data Source
AI summary
A flexible circuit having improved corrosion resistance and method therefor. The flexible circuit includes, a polymeric support substrate, a conductive layer providing tracing attached to a first surface of the support substrate, and lead beams in electrical communication with the tracing for attaching the flexible circuit to a micro-fluid ejection head. A plasma polymerized layer is deposited on at least a portion of the conductive layer to reduce corrosion of the conductive layer. The plasma polymerized layer may also improve adhesion between the flexible circuit and an adhesive use to attach the flexible circuit to a structure.