Light Emitting Device Stepped Support Member Thermal Stress

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Solution Overview

Problem

Existing light emitting devices face damage to the light transmissive member due to thermal expansion mismatch between components, leading to potential cracks and deformation.

Innovation Solution

The design includes a base with a frame and a cover featuring a support member with stepped portions, where the lens body is positioned on a higher step and the light transmissive portion on a lower step, minimizing the thermal expansion coefficient difference between these components and the main body, thereby reducing stress on the light transmissive portion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the light transmissive portion is joined with the cover to close the through-hole, then the cover structure is completed and light transmission is enabled, but the light transmissive member suffers damage due to thermal expansion mismatch

Engineering Contradiction:

Improvestructural integrityVSAvoidthermal expansion damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The support member acts as an intermediary component between the cover and the light transmissive portion. It provides a transition structure with stepped portions that accommodate thermal expansion differences, thereby protecting the light transmissive member from damage while maintaining structural integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The support member features stepped portions with different heights and positions, creating a gradient structure that accommodates thermal expansion. The first portion is positioned higher than the second portion, and the third portion is positioned lower than the second portion, allowing differential thermal movement without causing damage to the light transmissive portion.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If the cover is made rigid to maintain structural stability, then the cover can surround and protect the laser elements, but the cover deforms under thermal expansion stress

Engineering Contradiction:

Improvecover structural stabilityVSAvoidcover deformation

Core Design Contradiction:

Stability of the object's compositionVSShape

Solution Approach 1:

The support member is divided into multiple portions (first portion, second portion, third portion) with different heights and functions. This segmentation allows each portion to handle different aspects of structural support and thermal expansion, preventing overall cover deformation while maintaining stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The support member introduces a vertical dimension with stepped portions at different heights. The first portion is higher, the second portion is lower, and the third portion is even lower, creating a multi-level structure that accommodates thermal expansion in the vertical direction while maintaining horizontal structural stability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Device complexity

If the light transmissive portion is positioned to close the opening directly, then the structure is simplified, but stress concentration occurs due to thermal expansion mismatch

Engineering Contradiction:

Improvestructural simplicityVSAvoidthermal stress

Core Design Contradiction:

Device complexityVSStress or pressure

Solution Approach 1:

The support member with its stepped portions serves as an intermediary structure between the cover opening and the light transmissive portion. This intermediate structure distributes thermal stress across multiple levels, preventing stress concentration at the junction while maintaining relative structural simplicity.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration reduces damage to the light transmissive portion by minimizing stress exerted due to thermal expansion, enhancing the durability of the light emitting device.

Implementation Method 1

A difference between a thermal expansion coefficient of the light transmissive portion and a thermal expansion coefficient of the lens body is smaller than a difference between a thermal expansion coefficient of the light transmissive portion and a thermal expansion coefficient of the main body

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS11367994B2Light emitting device

Publication Date: 2022.06.21 NICHIA CORP

AI summary

A light emitting device includes: a base including: a main body, and a frame disposed on an upper surface of the main body; one or more laser elements disposed on the upper surface of the main body and positioned inward of the frame; and a cover including: a support member that is fixed to an upper surface of the frame and that has an opening inside the frame, and a light transmissive portion that is fixed to the support member and that is disposed so as to close the opening. A first interface, between the light transmissive portion and the support member, is located inward of and lower than a second interface, between the support member and the frame. A portion of the support member that extends at least from an outermost end of the first interface to an innermost end of the second interface has a constant thickness.