Membrane Keyboard Sensing Circuit for Thin Proximity Detection

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Solution Overview

Problem

Existing keyboard devices with proximity sensing functions use sheet metal layers as sensing layers, which are costly and increase the device thickness, making them less suitable for lighter and thinner designs.

Innovation Solution

A keyboard device with a membrane circuit board that includes a lower membrane layer, an upper membrane layer, and a sensing circuit pattern disposed over the upper membrane layer. The sensing circuit pattern consists of a surrounding wire and connecting wires that surround the key regions and connect between adjacent portions of the surrounding wire, respectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a sheet metal layer is used as a sensing layer in a keyboard device with proximity sensing function, then the proximity sensing function is achieved, but the cost increases and the overall thickness increases

Engineering Contradiction:

Improveproximity sensing functionVSAvoidcost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces expensive sheet metal sensing layers with inexpensive printed circuit board trace patterns. The sensing function is achieved through conductive traces formed on the PCB substrate using standard PCB manufacturing processes, eliminating the need for costly metal layers while maintaining proximity sensing capability.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes the mechanical sheet metal structure with an electronic circuit implementation. Instead of using a physical metal layer for sensing, the invention uses electrical trace patterns on the PCB that perform the same sensing function through electrical field detection, thereby reducing both cost and thickness.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If a sheet metal layer is used as a sensing layer in a keyboard device with proximity sensing function, then the proximity sensing function is achieved, but the overall thickness increases

Engineering Contradiction:

Improveproximity sensing functionVSAvoidoverall thickness

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent utilizes the thin PCB substrate itself as the sensing structure. The conductive traces are formed directly on the PCB layers, eliminating the need for additional thick metal sensing layers. This approach maintains the proximity sensing function while keeping the overall device thickness minimal, as the sensing function is integrated into the existing thin PCB structure.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent replaces the thick mechanical sheet metal sensing layer with thin electrical trace patterns on the PCB. The electrical traces provide the sensing function without requiring the physical thickness of a metal layer, thereby reducing the overall device thickness while maintaining sensing capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If a sheet metal layer is used as a sensing layer, then the proximity sensing function is achieved, but the device becomes less suitable for lighter and thinner designs

Engineering Contradiction:

Improveproximity sensing functionVSAvoiddevice weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent replaces heavy sheet metal with lightweight PCB trace patterns. The conductive traces are formed using standard PCB materials and processes, which are significantly lighter than metal layers, thereby reducing the overall device weight while maintaining the proximity sensing function.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes the heavy mechanical sheet metal structure with lightweight electrical trace patterns on the PCB. This substitution eliminates the need for dense metal layers while providing the same sensing function, thereby reducing device weight and making it more suitable for lightweight designs.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12327698B2Keyboard device

Publication Date: 2025.06.10 PRIMAX ELECTRONICS LTD

AI summary

A keyboard device includes a membrane circuit board and a support plate. The membrane circuit board has a plurality of key regions and a peripheral region surrounding the key regions. The membrane circuit board includes: a lower membrane layer; an upper membrane layer disposed over the lower membrane layer; and a sensing circuit pattern disposed over the upper membrane layer and in the peripheral region, in which the sensing circuit pattern includes a surrounding wire and at least one connecting wire, and the surrounding wire surrounds the key regions, and the at least one connecting wire is connected between two adjacent portions of the surrounding wire. The support plate is disposed beneath the membrane circuit board.