Single-Substrate Membrane Switch Using Variable Resistance Layer

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Solution Overview

Problem

Conventional membrane switches require two substrates and a flexible top layer, making them more expensive and thicker than desired, and they do not allow for rapid state changes without moving parts, which limits their application in space-constrained and cost-sensitive devices.

Innovation Solution

A membrane switch design featuring a single substrate with interdigital electrodes and a layer of variable resistance material that changes conductivity in response to applied force, eliminating the need for a separate flexible layer and enabling rapid state transitions without moving parts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a conventional membrane switch uses two substrates with a flexible top layer, then the switch can be actuated by pressing, but the switch becomes thicker and more expensive

Engineering Contradiction:

Improvemanufacturing costVSAvoidswitch thickness

Core Design Contradiction:

Ease of manufactureVSLength of stationary object

Solution Approach 1:

The patent combines the substrate and the variable resistance layer into a single integrated structure. The variable resistance layer is formed directly on the substrate, eliminating the need for a separate flexible top layer and reducing the overall switch thickness while maintaining the pressing actuation functionality.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent removes the flexible top layer from the conventional membrane switch structure. By extracting this component and replacing it with a variable resistance layer formed directly on the substrate, the switch achieves reduced thickness and lower manufacturing cost while retaining press-actuation capability.

Inventive Principle:

Principle #2Taking out (Extraction)

2Ease of operation

If a membrane switch uses a flexible top layer as a carrier for the shorting pad, then the switch can be actuated, but the switch requires more space and has moving parts

Engineering Contradiction:

Improveswitch actuationVSAvoidnumber of moving parts

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical pressing mechanism that moves a shorting pad with an electrical field-based mechanism. The variable resistance layer changes its resistance state in response to an applied electric field, eliminating the need for mechanical movement of parts while maintaining switch actuation functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses a variable resistance layer whose electrical properties dynamically change in response to an applied electric field. This dynamic electrical response replaces the static mechanical structure, allowing the switch to change state without physical movement of components.

Inventive Principle:

Principle #15Dynamics

3Reliability

If a membrane switch uses two substrates separated by a spacer layer, then the shorting pad is prevented from inadvertent contact, but the switch must be thicker

Engineering Contradiction:

Improveprevention of inadvertent shortingVSAvoidswitch thickness

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent uses a thin variable resistance layer formed directly on the substrate to provide the necessary electrical isolation and switching functionality. This thin film structure eliminates the need for a thick spacer layer while maintaining reliability by preventing inadvertent contact through its inherent electrical properties rather than physical separation.

Inventive Principle:

Principle #30Flexible shells and thin films

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 single-substrate membrane switch reduces manufacturing costs, minimizes thickness, and allows for rapid state changes with varying resistance based on applied force, enabling efficient and durable operation in thin-profile applications.

Implementation Method 1

a layer of a variable resistance material is in contact with the plurality of electrical poles. An electrical resistance of the layer of the variable resistance material to electrical current flow between the plurality of electrical poles varies as a function of a force applied against the layer of the variable resistance material

Methodology Applied

Scientific EffectPiezoresistive effect: Piezoresistive Effect

Data Source

PatentUS8368505B2Switch using variable resistance layer to control state

Publication Date: 2013.02.05 ALMAX MFG CORP

AI summary

An electrical membrane switch that is actuated by applying a force against a layer of a variable resistance material that overlies and is in direct contact with switch poles that are applied to and supported by a substrate. A gap is provided between the switch poles, and the layer extends across the gap. The substrate can be a circuit board with electrical traces formed thereon to convey electrical current to the switch poles. As a sufficient force is applied to the surface of the layer of the variable resistance material, its resistance changes from a relatively high value, in which the switch is in a non-conducting state, to a relatively low value, in which the switch is in a conductive state. A protective sheet can optionally be included over the variable resistance layer and can include graphics/text to indicate the position of each switch in an array and its function.