Flexible Thermistor Surface Height Matching on FPC

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Solution Overview

Problem

Existing temperature sensors on flexible boards face challenges with flexibility, leading to cracking and poor heat conduction, especially when detecting small heat sources, due to the rigidity of thermistor elements and mismatched thicknesses with the flexible board, resulting in reduced accuracy and potential damage.

Innovation Solution

A flexible thermistor with a metal base and a thin thermistor layer, paired with split electrodes, is mounted on a flexible board with a cover layer, ensuring the thermistor's surface height matches the cover layer's, allowing direct contact with temperature objects while reducing stress and enhancing flexibility, thus improving detection accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a thin temperature information detecting element is arranged on a flexible board, then the stress load on the power generating element is limited, but cracks develop in the temperature information detecting element when load is applied

Engineering Contradiction:

Improvestress load resistanceVSAvoidcrack resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent uses a flexible printed circuit board (FPC) with a thin film structure to support the temperature information detecting element. The FPC's flexibility allows it to conform to curved surfaces and absorb stress, preventing cracks in the detecting element while maintaining thin profile for low stress transmission to the power generating element.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent employs a composite structure combining the temperature information detecting element with the flexible printed circuit board. This composite design integrates the rigid detecting element with the flexible FPC, allowing the combination to withstand bending and stress without cracking, while maintaining the detecting element's functionality.

Inventive Principle:

Principle #40Composite materials

2Device complexity

If the temperature information detecting element is received inside the flexible board, then the structure is compact, but the temperature information detecting element does not directly contact the temperature detection object, resulting in poor heat conduction

Engineering Contradiction:

Improvestructural compactnessVSAvoidheat conduction efficiency

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent extracts the temperature information detecting element from the interior of the flexible board and positions it on the outer surface of the FPC. This extraction allows the detecting element to directly contact the temperature detection object, improving heat conduction efficiency while the FPC maintains structural compactness through its flexible nature.

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of manufacture

If a commonly used chip component is mounted on the flexible board, then the temperature sensor can be integrated, but the chip component's thickness is very large compared to the flexible board, causing cracks when pressure is applied

Engineering Contradiction:

Improveintegration capabilityVSAvoidpressure resistance

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent replaces the rigid chip component with a temperature information detecting element designed as a thin film structure that is integrated with the flexible printed circuit board. This thin film design matches the flexibility and thickness of the FPC, allowing the assembly to withstand pressure without cracking, while maintaining ease of integration through standard FPC manufacturing processes.

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 solution enables precise temperature detection with high thermal responsiveness and reduced risk of cracking, even on curved surfaces, by matching the thermistor's surface height with the cover layer's, ensuring effective contact and improved accuracy, especially for small heat sources.

Implementation Method 1

the temperature information detecting element does not directly contact a temperature detection object, resulting in poor heat conduction

Methodology Applied

Scientific EffectThermal energy conduction: Conduction (thermal)

Implementation Method 2

a thermistor element used as a temperature sensor is mounted on a flexible board

Methodology Applied

Scientific EffectThermistor effect: Thermistor

Data Source

PatentUS9316546B2Temperature sensor and temperature sensor attaching structure

Publication Date: 2016.04.19 MURATA MFG CO LTD

AI summary

A flexible board includes a base layer, a wiring conductor layer that is located on the base layer, and a cover layer that is stacked over the base layer and covers the wiring conductor layer. A portion of the wiring conductor layer defines connecting portions that connect each of split electrodes of a flexible thermistor. The cover layer includes an opening that exposes the connecting portions, and receives the flexible thermistor. The split electrodes of the flexible thermistor are mounted on the connecting portions of the wiring layer. The height of the exposed surface of the flexible thermistor from the opening is substantially equal to the height of the surface of the cover layer.