Polyimide Substrate Force Sensing Resistor for VR

Solution Overview

Problem

Existing hand-held video game controllers with force sensing resistors (FSRs) exhibit crude response curves and are limited by the use of mylar substrates, which are bulky, difficult to miniaturize, and cannot withstand high temperatures, making them unsuitable for virtual reality applications.

Innovation Solution

A FSR constructed with a polyimide substrate and a resistive, flexible second substrate, where conductive material on the first substrate comes into contact with resistive material on the second substrate under applied force, providing a more accurate and repeatable Force vs. Resistance response curve, allowing for direct soldering and reduced manufacturing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If mylar substrate is used in FSR construction, then manufacturing is easier and costs are lower, but the FSR becomes bulky, difficult to miniaturize, and cannot withstand high temperatures

Engineering Contradiction:

Improveease of manufactureVSAvoidfootprint

Core Design Contradiction:

Ease of manufactureVSVolume of moving object

Solution Approach 1:

The patent changes the substrate material from mylar to polyimide, which has different physical properties including higher temperature resistance and flexibility that enables miniaturization while maintaining manufacturability through direct soldering techniques

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite structure with polyimide substrate combined with conductive and resistive materials to create an FSR that achieves both small footprint and high temperature resistance while remaining manufacturable

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If mylar substrate is used in FSR construction, then manufacturing costs are reduced, but the FSR cannot tolerate high temperatures of reflow oven

Engineering Contradiction:

Improvemanufacturing costVSAvoidtemperature resistance

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The patent changes the substrate material from mylar to polyimide, which has different physical properties including higher temperature resistance and flexibility that enables miniaturization while maintaining manufacturability through direct soldering techniques

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical connector system (header connector) with direct soldering of the FSR to the circuit board, which eliminates the need for bulky connectors and enables the use of polyimide substrate that can withstand reflow oven temperatures

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Temperature

If PCB substrate is used in FSR construction, then the FSR can withstand high temperatures, but the response curve becomes crude and non-monotonic

Engineering Contradiction:

Improvetemperature resistanceVSAvoidresponse curve accuracy

Core Design Contradiction:

TemperatureVSMeasurement precision

Solution Approach 1:

The patent changes the substrate material from PCB to polyimide, which provides both high temperature resistance and maintains a smooth, monotonic response curve for accurate force measurement in VR applications

Inventive Principle:

Principle #35Parameter changes

4Ease of manufacture

If mylar-based FSR with header connector is used, then manufacturing is simpler, but the FSR consumes large footprint and is difficult to miniaturize

Engineering Contradiction:

Improveease of manufactureVSAvoidfootprint

Core Design Contradiction:

Ease of manufactureVSArea of stationary object

Solution Approach 1:

The patent replaces the mechanical connector system (header connector) with direct soldering of the FSR to the circuit board, which eliminates the need for bulky connectors and enables the use of polyimide substrate that can withstand reflow oven temperatures

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 polyimide-based FSR offers improved sensitivity, reduced hysteresis, and higher repeatability, enabling more precise analog inputs suitable for virtual reality systems, reducing user fatigue, and allowing for cost-effective manufacturing.

Implementation Method 1

the force sensing resistor (FSR), which uses variable resistance to measure an amount of force applied to the FSR

Methodology Applied

Scientific EffectVariable resistance: Electrical Resistance

Data Source

PatentUS11465041B2Force sensing resistor (FSR) with polyimide substrate, systems, and methods thereof

Publication Date: 2022.10.11 VALVE CORPORATION

AI summary

A force sensing resistor (FSR) that is constructed with a first substrate made of polyimide disposed underneath a second substrate that is resistive and flexible. A handheld controller for an electronic system may include the FSR having a first substrate made of polyimide. The FSR may be mounted on a planar surface of a structure within the controller body, such as a structure mounted within a handle of the controller body, and/or a structure that is mounted underneath at least one thumb-operated control that is included on a head of the controller body. The FSR may be configured to measure a resistance value that corresponds to an amount of force applied to an outer surface of the handle and/or an amount of force applied to the at least one thumb-operated control.