Lead Frame Metal Layer for LED Package Moisture Protection
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Solution Overview
Problem
Group III-V nitride semiconductor light emitting diodes and laser diodes face issues with moisture ingress and oxidation of lead frames due to material differences and thermal expansion mismatches, leading to electrical characteristic deterioration and heat dissipation problems.
Innovation Solution
A light emitting device package design featuring a housing with a cavity, a lead frame with sections electrically connected to the device and extending outside, and a metal layer or sealant to prevent moisture ingress and oxidation, using materials like Polyphthalamide resin and metal or alloy lead frames with plating layers, and applying a metal layer or sealant to create a barrier between the lead frames and the housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lead frame is directly exposed to the external environment, then the electrical connection is simple and the structure is compact, but moisture ingress and oxidation occur leading to electrical characteristic deterioration
Solution Approach 1:
A metal layer is introduced as an intermediary component between the lead frame and the external environment. This metal layer serves as a protective barrier that prevents moisture ingress and oxidation while maintaining electrical conductivity, thus resolving the contradiction between reliability and structural simplicity
Solution Approach 2:
The package structure employs composite materials including the lead frame, metal layer, and housing material (Polyphthalamide resin). These composite materials work together to provide both electrical functionality and environmental protection, addressing the reliability issue without significantly increasing structural complexity
2Reliability
If the lead frame penetrates the housing without protection, then the manufacturing process is simple, but thermal expansion mismatch causes bonding deterioration and heat dissipation problems
Solution Approach 1:
The metal layer changes the physical and chemical parameters of the lead frame surface, providing better thermal and electrical conductivity. This parameter change allows for improved heat dissipation and bonding strength while maintaining a relatively simple manufacturing process through standard deposition techniques
Solution Approach 2:
The metal layer acts as a thermal expansion buffer between the lead frame and the housing. By having different thermal expansion coefficients, the metal layer accommodates thermal stress during temperature changes, preventing bonding deterioration and maintaining manufacturing simplicity
3Reliability
If no protective layer is applied to the lead frame, then the device structure is simple and cost-effective, but oxidation occurs leading to increased electrical resistance and performance degradation
Solution Approach 1:
The metal layer serves as an intermediary protective barrier that specifically targets oxidation prevention. This single protective layer maintains electrical conductivity while protecting against environmental degradation, resolving the contradiction between reliability and structural simplicity more effectively than multiple protective layers would
Solution Approach 2:
The metal layer is designed as a thin, cost-effective protective barrier that can be applied through economical deposition processes. While the layer itself is thin and potentially replaceable, it provides sufficient protection against oxidation to maintain electrical conductivity without requiring complex or expensive protective structures
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
Prevents oxidation and moisture ingress, maintaining the unique electrical characteristics of the lead frames and enhancing heat radiation and bonding, thereby improving the reliability and performance of the light emitting device package.
Implementation Method 1
a metal layer positioned on an area defined by a distance which is distant from the housing in the second section of the lead frame
Implementation Method 2
an sealant for blocking an area from outside air, which is defined by a distance from the housing in the second section of the lead frame
Implementation Method 3
The light emitting diode changes electricity to light or infrared light by using its characteristics as a combination semiconductor
Data Source
AI summary
Embodiments include a light emitting device package. The light emitting device package comprises a housing including a cavity; a light emitting device positioned in the cavity; a lead frame including a first section electrically connected to the light emitting device in the cavity, a second section, which penetrates the housing, extending from the first section and a third section, which is exposed to outside air, extending from the second section; and a metal layer positioned on an area defined by a distance which is distant from the housing in the second section of the lead frame.