Segmented Plating Layer for Light Emitting Device Heat Dissipation
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Solution Overview
Problem
Conventional light emitting devices with semiconductor elements face challenges in heat dissipation and solder adhesion due to the diffusion of copper into silver plating layers, leading to reduced reflectivity and increased oxidation, which affects the overall performance and reliability of the devices.
Innovation Solution
A light emitting device design featuring a lead with a copper metal board plated with a first layer containing silver and nickel on the edge and a second layer without nickel beneath the light emitting element, enhancing heat dissipation and solder adhesion while preventing copper diffusion and oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the lead is plated with a silver layer to improve reflectivity, then the reflectivity is improved, but copper diffusion into the silver layer occurs leading to reduced reliability
Solution Approach 1:
The plating layer is segmented into multiple functional layers: a nickel underlayer for copper diffusion barrier, a silver layer for reflectivity, and optionally a solder layer for bonding. This segmentation allows each layer to perform its specific function without interfering with others, resolving the contradiction between reflectivity and copper diffusion resistance.
Solution Approach 2:
The nickel layer acts as an intermediary between the copper metal board and the silver plating layer. It prevents direct contact and diffusion between copper and silver while allowing the silver layer to maintain its reflectivity function. The nickel layer mediates the interaction between these two materials to eliminate the harmful copper diffusion effect.
2Reliability
If the lead is plated with nickel underlayer to prevent copper diffusion, then the reliability is improved, but the heat dissipation capability deteriorates
Solution Approach 1:
Different regions of the lead structure are assigned different plating qualities: the nickel underlayer provides copper diffusion barrier where needed, while the silver layer provides both reflectivity and superior heat dissipation. The copper metal board itself provides the primary heat dissipation path. This local quality differentiation allows the system to achieve both reliability and heat dissipation performance.
Solution Approach 2:
The lead structure uses a composite plating system combining nickel and silver layers on a copper metal board. Each material contributes its superior properties: copper for heat dissipation, nickel for diffusion barrier, and silver for reflectivity and additional heat dissipation. The composite structure achieves overall performance that exceeds individual materials.
3Illumination intensity
If the silver plating layer is made thicker to improve reflectivity, then the reflectivity is improved, but the solder adhesion deteriorates
Solution Approach 1:
The plating structure is segmented into distinct functional layers with the silver layer optimized for reflectivity and a separate solder layer or nickel layer providing solder adhesion. This segmentation allows the silver layer to be thick enough for optimal reflectivity without compromising solder adhesion, as the adhesion function is handled by the nickel or solder layer.
Solution Approach 2:
The nickel layer serves as an intermediary between the silver plating layer and the solder joint. It provides a surface that bonds well with solder while allowing the silver layer to maintain its reflectivity properties. This intermediary layer resolves the contradiction by decoupling the reflectivity function from the adhesion function.
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 improves heat dissipation and maintains solder adhesion, reducing the risk of copper diffusion and oxidation, thereby enhancing the performance and reliability of the light emitting device.
Implementation Method 1
Each of the leads includes a plating layer... preventing copper diffusion
Implementation Method 2
a light emitting device in which a silver-plated lead is used, with the light emitting device having improved heat dissipation
Implementation Method 3
reducing the risk of copper diffusion and oxidation
Data Source
AI summary
A light emitting device according to one aspect includes a resin package and a light emitting element. The resin package includes a molded resin part defining a part of a recessed portion, and a pair of leads. The leads are exposed from the molded resin part at a bottom surface of the recessed portion. Each of the leads includes a plating layer and exposed from the molded resin part at a lower surface of the resin package. A height of a first part of the plating layer exposed from the lower surface of the resin package and adjacent to an edge of a corresponding one of the leads is different from a height of a second part of the plating layer exposed from the lower surface of the resin package. The light emitting element is mounted on the bottom surface of the recessed portion.