Light Emitting Device Sealing Resin Segmentation for Corrosion Resistance
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Solution Overview
Problem
Light emitting devices with silver-containing layers are susceptible to discoloration and corrosion due to sulfur-containing gases penetrating through cracks between leads and resin packages, caused by differing coefficients of thermal expansion, leading to reflectivity degradation.
Innovation Solution
A light emitting device design featuring a silver-containing layer on leads secured by a resin molded body, covered by an inorganic protective film and a sealing resin with a harder second resin layer at boundaries to prevent gas penetration and corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective film is applied to cover the silver-containing layer, then corrosion resistance is improved, but the protective film is susceptible to cracking due to different coefficients of thermal expansion between leads and resins
Solution Approach 1:
The sealing resin is divided into two distinct layers: a first resin layer that covers the light emitting element and allows thermal expansion, and a second resin layer with higher hardness that covers the boundaries between the resin molded body and leads. This segmentation allows each layer to perform its specific function - the first layer accommodates thermal stress while the second layer provides crack-resistant sealing at critical boundaries.
Solution Approach 2:
Different resin materials with different properties are applied to different locations. The first resin (softer, more flexible) is applied to the central area covering the light emitting element where thermal expansion occurs, while the second resin (harder, more rigid) is applied specifically at the boundaries between leads and resin molded body where crack resistance is most critical. This local differentiation optimizes both protection and stress accommodation.
2Object-affected harmful factors
If the sealing resin covers the entire base surface, then gas penetration is suppressed, but the different coefficients of linear expansion between leads and protective films cause cracking
Solution Approach 1:
The sealing resin is segmented into two functional layers with different properties. The first resin layer provides baseline sealing while accommodating thermal expansion, and the second harder resin layer provides enhanced crack resistance at the boundaries. This segmentation allows the system to maintain both gas barrier functionality and mechanical strength.
Solution Approach 2:
The sealing structure uses a composite of two different resin materials with complementary properties. The first resin provides flexibility and adhesion, while the second resin provides hardness and crack resistance. This composite approach creates a sealing system that can simultaneously prevent gas penetration and withstand thermal expansion stresses.
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 suppresses discoloration and corrosion of the silver-containing layer, maintaining reflectivity and extending the lifespan of light emitting devices in corrosive environments.
Implementation Method 1
a protective film made of an inorganic material that covers the upper surface of the base
Implementation Method 2
a second resin, having a higher hardness than the first resin, that covers the boundaries between the resin molded body and the leads. This suppresses the penetration of sulfur-containing gas
Data Source
AI summary
A light emitting device has a base comprising at least one pair of leads having a silver-containing layer on their surfaces and being secured by a resin molded body, a light emitting element mounted on said leads, a protective film made of an inorganic material that covers the upper surface of said base, and a sealing resin disposed on the base surface via said protective film. The sealing resin has a first resin that covers said light emitting element, and a second resin having a higher hardness than said first resin that covers the boundaries between said resin molded body and said leads.