Flexible Keyboard Circuit Sealing for Waterproof Tactile Keys
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Solution Overview
Problem
Conventional human interface devices, such as keyboards, are vulnerable to liquid and solid particle exposure, leading to malfunction and damage, and fail to withstand disinfection and extreme temperatures, posing health risks due to contamination and infection risks from microbial bacteria like MRSA.
Innovation Solution
A waterproof keyboard design featuring a flexible circuit with multiple sealed air chambers and a hermetically sealed housing, eliminating the need for external vents and using biaxially-oriented polyethylene terephthalate and acrylic-based adhesive layers for enhanced chemical resistance and tactile feedback, along with a controller for visual indicators and sealing mechanisms to prevent liquid ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional keyboard designs are used, then tactile feedback and switch operation are achieved, but liquid ingress causes circuit shorting and device failure
Solution Approach 1:
The keyboard circuit board is segmented into multiple isolated sealed chambers, each containing individual switches. This segmentation prevents liquid from traveling across the entire circuit board and causing widespread shorting, as liquids are contained within individual sealed chambers that prevent ingress to the electrical components.
Solution Approach 2:
A hydrophobic coating is applied as an intermediary layer between the liquid environment and the electrical circuitry. This coating acts as a mediator that repels liquids while allowing the keyboard to maintain its tactile feedback mechanisms and switch operations, preventing liquid-circuit contact without isolating the entire device in a bulky enclosure.
2Ease of operation
If keyboards are designed with vents for air movement, then tactile feedback is maintained, but liquid can enter through vents and damage internal circuitry
Solution Approach 1:
Flexible membranes with integrated switch mechanisms replace traditional vent openings. These thin film structures maintain tactile feedback by allowing key actuation while the hydrophobic coating on the membrane surface prevents liquid penetration, eliminating the need for separate vents that would compromise waterproofing.
Solution Approach 2:
The hydrophobic coating serves as an intermediary layer on the flexible membrane, allowing tactile interaction while blocking liquid ingress. This coating enables the membrane to function as both a tactile interface and a liquid barrier, eliminating the need for vents that would allow liquid entry.
3Reliability
If keyboards are exposed to cleaning agents and disinfectants, then sanitation is achieved, but conventional keyboards suffer chemical degradation and microbial contamination
Solution Approach 1:
The hydrophobic coating acts as a chemical-resistant intermediary layer that protects the underlying circuit board and components from direct contact with cleaning agents and disinfectants. This coating is specifically designed to resist chemical degradation while allowing the keyboard surface to be sanitized, preventing both chemical damage and microbial contamination of internal components.
Solution Approach 2:
The hydrophobic coating provides a sacrificial protective layer that can be repeatedly exposed to harsh cleaning agents without compromising the underlying electronics. This coating is designed to withstand extensive sanitization cycles, effectively making the keyboard surface disposable in terms of cleaning exposure while preserving the permanent electronic components.
4Reliability
If sealed chambers are used to prevent liquid ingress, then waterproofing is achieved, but air pressure equalization during key actuation becomes problematic
Solution Approach 1:
The flexible membranes forming the sealed chambers are designed with controlled compliance to allow minimal expansion and contraction during key actuation. This flexibility enables air pressure equalization within each sealed chamber without compromising the waterproof seal, as the membrane can accommodate pressure changes while maintaining liquid barrier integrity.
Solution Approach 2:
By segmenting the keyboard into multiple small sealed chambers rather than one large sealed enclosure, the air pressure changes during key actuation are minimized within each chamber. This segmentation reduces the overall volume subject to pressure changes, making pressure equalization easier while maintaining effective waterproofing.
Data Source
AI summary
A waterproof keyboard includes a housing having keyboard buttons, and a flexible keyboard circuit carried within the housing. The flexible keyboard circuit includes a first polymer layer, and an electrically conductive material layer on the first polymer layer to define switches and connections. The switches are aligned with the keyboard buttons. The flexible keyboard circuit also includes a second polymer layer over the first polymer layer and the electrically conductive material layer, and an adhesive layer between the first polymer layer and the second polymer layer and defining sealed air chambers. Subsets of the switches are respectively within the sealed air chambers. The waterproof keyboard also includes a controller to be coupled to the flexible keyboard circuit.