Secure Keyboard with Folded Flexible Circuit

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Solution Overview

Problem

Conventional keyboards used for entering sensitive data lack comprehensive security measures, as the key press detection contacts are easily accessible, making them vulnerable to intrusion and data theft.

Innovation Solution

A flexible printed circuit with a folded connection portion and internal key press detection contacts, combined with deformable domes in an inverted configuration, forms a protective enclosure around the sensitive areas, enhancing security without the need for additional protective circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If contacts are arranged on the external face of the connection printed circuit for easy key press detection, then key press detection is simplified, but security is compromised as contacts become easily accessible to intruders

Engineering Contradiction:

Improvekey press detectionVSAvoidintrusion vulnerability

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent inverts the conventional arrangement by placing contacts on the internal face of the connection printed circuit instead of the external face. This inversion shields the contacts from direct external access while maintaining electrical functionality, as the flexible printed circuit can still transmit key press signals from the external side through its deformable structure.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent utilizes the third dimension by folding the connection portion of the flexible printed circuit underneath the key press detection portion. This creates a protective enclosure that shields the contacts from all sides (top, bottom, and sides), transforming a two-dimensional circuit layout into a three-dimensional protective structure that maintains electrical connectivity while enhancing security.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Strength

If a rigid printed circuit is used for structural stability, then mechanical strength is improved, but flexibility and compactness are reduced

Engineering Contradiction:

Improvemechanical stabilityVSAvoidcircuit flexibility

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent employs a flexible printed circuit instead of a rigid one, utilizing flexible materials that can deform elastically when keys are pressed. This flexible circuit maintains mechanical stability through its material properties and structural design while enabling the connection portion to fold underneath the key press detection portion, creating a compact protective enclosure without requiring additional rigid components.

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

This design significantly increases keyboard security by shielding key press detection contacts from direct access, reducing the risk of intrusion while maintaining tactile feedback and mechanical stability, and allows for a more compact and cost-effective structure.

Implementation Method 1

the flexible printed circuit can undergo local deformations: it therefore does not hinder the communication of the pressure force exerted on a key (11)

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

the dome undergoes a sudden transformation by crashing, and the user immediately feels that his pressing of the key has indeed been taken into account

Methodology Applied

Scientific EffectMechanical deformation and phase transition: Deformation

Data Source

PatentEP3379389B1Secure keyboard for electronic data entry device

Publication Date: 2020.08.19 COMPAGNIE INDUSTRIELLE ET FINANCIERE D INGENIERIE INGENICO SA

Figure 1a~1c
Figure 2~4

AI summary

The invention relates to a keypad for an electronic data entry device. Such a keypad comprises: - a plurality of keys defining a key layer; - a connecting printed circuit board, including a key press detection portion having an outer face oriented towards the key layer, and an inner face opposite the outer face; - for each key in the key layer, an interconnecting element and a pair of contacts on the connecting printed circuit board, the interconnecting element being intended to ensure the electrical interconnection of the contacts of said contact pair when the associated key is pressed. According to the invention, the connecting printed circuit board is a flexible printed circuit board which further comprises a connecting portion forming a fold under the inner face of the key press detection portion, and said pair of contacts is disposed on said inner face.