Light Emitting Device Package Anti-Fracture Layer Thermal Stress
Solution Overview
Problem
Conventional light emitting device packages face durability issues due to thermal expansion mismatch between the heat dissipation member and the package body, leading to potential cracking of the ceramic layer and reduced hermetic seal durability, especially under high humidity or extended operation conditions.
Innovation Solution
Incorporating an anti-fracture layer made of a second ceramic material with a specific thickness and open region design, which overlaps with the heat dissipation member, and using a third ceramic layer for thermal contact between the light emitting device and the heat dissipation member, formed from materials like copper or tungsten, to manage thermal stress and maintain package integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ceramic layer is provided over the heat dissipation member to prevent damage from thermal expansion, then the light emitting device is protected from thermal damage, but stress is applied to the ceramic layer during co-firing due to coefficient of thermal expansion mismatch, causing cracking and reduced hermetic seal durability
Solution Approach 1:
A buffer layer is introduced between the heat dissipation member and the ceramic layer to act as an intermediary that absorbs and distributes thermal stress. This buffer layer has thermal expansion characteristics that are intermediate between the heat dissipation member and the ceramic layer, preventing stress concentration and cracking in the ceramic layer while maintaining thermal protection of the light emitting device.
Solution Approach 2:
The package structure uses a composite material system consisting of the heat dissipation member, buffer layer, and ceramic layer with different thermal expansion properties. This composite structure is designed to manage differential thermal expansion through proper material selection and layer thickness optimization, resolving the contradiction between thermal protection and structural integrity.
2Temperature
If the heat dissipation member is made of highly thermally conductive material to emit heat, then heat dissipation efficiency is improved, but thermal expansion of the heat dissipation member causes damage to the light emitting device
Solution Approach 1:
The buffer layer serves as a mediator between the highly thermally conductive heat dissipation member and the light emitting device. It allows efficient heat transfer from the heat dissipation member while providing mechanical isolation to prevent damage from thermal expansion, thus resolving the contradiction between heat dissipation efficiency and device durability.
Solution Approach 2:
The buffer layer changes the thermal and mechanical parameters of the heat transfer path. It maintains adequate thermal conductivity for heat dissipation while modifying the mechanical coupling characteristics to reduce stress transmission, thereby protecting the light emitting device from thermal expansion damage.
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 enhances the hermetic seal durability and reliability of the light emitting device package by effectively managing thermal expansion stress, preventing cracking, and maintaining package integrity even under challenging conditions.
Implementation Method 1
a heat dissipation member disposed in the package body with thermally contacting to the light emitting device
Implementation Method 2
stress may be applied to the ceramic layer 120 above the boundary of the heat dissipation member 130 and the package body 110b due to mismatch between the coefficient of thermal expansion of the heat dissipation member 130 and that of the package body 110b
Data Source
AI summary
A light emitting device package including a package body including a first cavity and a second cavity, a pad disposed on a bottom surface of the first cavity, a light emitting device disposed on the second cavity electrically connected to the pad, a heat dissipation member inserted into the package body, the heat dissipation member including a body and expanded portions disposed at a partial edge region of the body and electrode patterns disposed at the package body, wherein the package body has an upper portion and a lower portion disposed under the upper portion, wherein the first cavity including side surfaces and a bottom surface, wherein the second cavity provided in the bottom surface of the first cavity.