Flexible LED with Thermocompression Bonding for Bending Reliability

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Solution Overview

Problem

Conventional transparent light emitting devices using LEDs suffer from reduced luminous intensity and short circuits when bent, due to electrical connections failing under stress and temperature changes.

Innovation Solution

A light emitting device design featuring a specific ratio of substrate area to light emitting layer area and electrode placement, combined with a thermocompression bonding process using a Vicat softening temperature-controlled resin, ensures reliable electrical and mechanical connections between conductive circuit layers and electrodes, maintaining light emission even under bending and high temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If thermocompression bonding is used to connect electrodes and conductive circuit layers, then electrical connection is achieved, but the device becomes susceptible to short circuits and luminous intensity reduction when bent

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidshort circuit and luminous intensity reduction under bending

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by performing thermocompression bonding during the manufacturing process to pre-establish robust electrical connections between electrodes and conductive circuit layers. This preliminary bonding creates a mechanically strong interface that can withstand subsequent bending operations, preventing short circuits and maintaining luminous intensity. The bonding is done before the device is put into service, ensuring connections are optimized for both electrical conductivity and mechanical durability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent utilizes parameter changes by carefully controlling the Vicat softening temperature of the resin used in thermocompression bonding. By selecting a resin with appropriate softening temperature characteristics, the bonding process can be optimized to create strong electrical connections without damaging the LED components. The temperature parameter is precisely controlled during bonding to ensure reliable connection while maintaining the device's flexibility and resistance to bending-induced failures.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If flexible transparent resin substrates are used, then adaptability and flexibility are enhanced, but electrical connections become more vulnerable to stress and temperature changes

Engineering Contradiction:

Improveflexibility and adaptabilityVSAvoidelectrical connection stability under stress

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent addresses this contradiction by changing the thermal parameter of the bonding resin, specifically selecting materials with appropriate Vicat softening temperatures. This parameter change allows the resin to remain flexible at operating temperatures while providing sufficient thermal and mechanical stability during bonding and service. The resin maintains its flexibility for adaptability while the controlled softening temperature ensures reliable electrical connections under stress and temperature variations.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite materials by combining flexible transparent resin substrates with thermocompression-bonded conductive circuit layers and electrodes. This composite structure integrates the flexibility of the resin with the electrical conductivity and mechanical strength of the bonded layers, creating a device that is both adaptable and reliable under various operating conditions including bending and temperature changes.

Inventive Principle:

Principle #40Composite materials

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 effectively prevents short circuits and maintains luminous intensity across various temperatures and bending conditions, enhancing the reliability and flexibility of the light emitting device.

Implementation Method 1

Electrical connection of the electrodes of the LED chips and the conductive circuit layers, is realized when a stack of the first transparent insulating substrate, the LED chips, and the second transparent insulating substrate is subjected to thermocompression bonding

Methodology Applied

Scientific EffectThermocompression bonding:

Implementation Method 2

a thermocompression bonding process using a Vicat softening temperature-controlled resin, ensures reliable electrical and mechanical connections

Methodology Applied

Scientific EffectVicat softening temperature:

Data Source

PatentUS9799811B2Light emitting device

Publication Date: 2017.10.24 NICHIA CORP

AI summary

A light emitting device of an embodiment includes first and second light transmissive support bodies, and a light emitting diode is disposed between the bases. The light emitting diode includes a first semiconductor layer provided on a first surface (area S1) of a substrate, a light emitting layer (area S2), and a second semiconductor layer. A first electrode in a pad shape is formed on the second semiconductor layer. The light emitting diode has a shape satisfying a relation of “1≦S1/S2≦−(3.46/H)+2.73”, where H is a distance from the first surface of the substrate to a surface of the first electrode.