Light Emitting Device Lead Frame Gap Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Light-emitting devices experience variations in light distribution over time due to thermal stress and peeling between the lead frame and light-transmitting resin, which can lead to corrosion and inefficient light extraction, and existing solutions either fail to prevent peeling or increase manufacturing costs.
Innovation Solution
A light-emitting device design featuring a lead frame with a recessed portion and a gap between the lead frame and light-transmitting resin, where the gap's width is longer than the main wavelength of light, and an adhesion-imparting agent is applied to ensure close contact between the lead frame and resin, preventing peeling and corrosion without additional sealing members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the adhesiveness between the lead frame and the light-transmitting resin is lowered to reduce thermal stress, then the deterioration of the light-emitting element due to thermal stress is prevented, but peeling occurs between the lead frame and the light-transmitting resin due to heat or light
Solution Approach 1:
The patent applies different adhesiveness requirements to different regions of the lead frame. The first lead frame portion (contacting the light-emitting element) has low adhesiveness to reduce thermal stress, while the second lead frame portion (exposed region) has high adhesiveness to prevent peeling. This local differentiation resolves the contradiction between reducing thermal stress and preventing peeling.
Solution Approach 2:
The lead frame is divided into two distinct portions with different adhesiveness characteristics. The first portion near the light-emitting element has reduced adhesiveness to minimize thermal stress, while the second portion in the exposed region maintains high adhesiveness to prevent peeling. This segmentation allows each region to fulfill its specific functional requirement.
2Reliability
If a light-transmitting resin having low adhesiveness is used to suppress thermal stress, then thermal stress on the light-emitting element is reduced, but water or flux enters inside from the gap between the lead frame and the light-transmitting resin to corrode the light-emitting element or the lead frame
Solution Approach 1:
The patent creates a localized high-adhesiveness region at the exposed portion of the lead frame to prevent water and flux entry, while maintaining low adhesiveness in the recessed portion to reduce thermal stress. This local quality differentiation addresses both the thermal stress resistance and corrosion protection requirements.
Solution Approach 2:
The patent introduces an adhesion promoter as an intermediary substance applied to the exposed region of the lead frame. This promoter enhances the adhesiveness between the lead frame and the light-transmitting resin at the exposed portion, creating a barrier against water and flux penetration without affecting the thermal stress characteristics in the recessed portion.
3Object-affected harmful factors
If a sealing member is added to enhance adhesiveness and prevent water or flux entry, then protection against corrosion is improved, but manufacturing time and production cost increase
Solution Approach 1:
The lead frame itself serves the dual function of structural support and sealing by having differentiated adhesiveness in different regions. The exposed portion with high adhesiveness acts as its own seal against water and flux, eliminating the need for additional sealing members and reducing manufacturing complexity.
Solution Approach 2:
The lead frame is designed to perform multiple functions: it provides structural support, manages thermal stress through low-adhesiveness regions, and prevents corrosion through high-adhesiveness exposed portions. This multi-functionality eliminates the need for separate sealing components, simplifying the overall device structure and manufacturing process.
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 design effectively prevents variations in light distribution and corrosion, enhancing light extraction efficiency and maintaining device reliability over time without increasing manufacturing costs.
Implementation Method 1
A gap is provided between the lead frame and the light-transmitting resin at an inner side surface of the recessed portion, the gap having a width longer than a main wavelength of light from the light-emitting element
Implementation Method 2
there are the following two cases for this. One results from the deterioration of a light-emitting element due to thermal stress and the other one results from peeling between the lead frame and the light-transmitting resin due to heat or light
Implementation Method 3
JP-A-H11-103097 and JP-A-2004-88002 propose to add a member for enhancing the adhesiveness between the lead frame and the light-transmitting resin
Data Source
AI summary
A light-emitting device includes lead frames, a light-emitting element placed on a bottom of a recessed portion formed at one of the lead frames, and a light-transmitting resin covering the light-emitting element. The lead frames have a covered region which is covered with the light-transmitting resin and an exposed region exposed out of the light-transmitting resin. The light-emitting device has a gap between the lead frame and the light-transmitting resin at an inner side surface of the recessed portion, the gap having a width longer than a main wavelength of light from the light-emitting element. The lead frame is in close contact with the light-transmitting resin at an end of the covered region, which is located in a boundary with the exposed region or in the vicinity of the boundary within the covered region.