LED Joint Body Structure for Thermal Shock Bonding Strength
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Solution Overview
Problem
Existing joint bodies used in light source devices with LEDs face challenges in maintaining high bonding strength between the substrate and the heat dissipating member, leading to degradation over time.
Innovation Solution
A joint body configuration is introduced, featuring a substrate with a base member and a metal layer, a nickel layer, a composite layer containing a mix of nickel and solder, and a solder layer, with the nickel extending to form protrusions and recesses, and an aluminum layer distributed between the composite and solder layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a simple solder layer is used to join the substrate and heat dissipating member, then the manufacturing process is simple, but the bonding strength degrades over time under thermal stress
Solution Approach 1:
The joint body is segmented into multiple functional layers: a nickel layer (11) for mechanical anchoring, a composite layer (15) with mixed nickel and solder for intermediate bonding, and a solder layer (13) for final joining. This segmentation allows each layer to perform its specific function optimally, preventing bonding strength degradation that would occur with a simple single-layer solder joint.
Solution Approach 2:
The composite layer (15) is formed by mixing nickel particles with solder material, creating a composite structure that combines the high strength and thermal stability of nickel with the bonding capabilities of solder. This composite material approach resolves the contradiction by providing both manufacturing feasibility and long-term bonding reliability under thermal stress.
2Reliability
If a multi-layer structure with composite layer is used, then the bonding strength and thermal shock resistance are improved, but the manufacturing complexity increases
Solution Approach 1:
The nickel layer (11) is formed on the substrate surface before applying the solder material. This preliminary action creates a prepared surface that controls the mixing process, allowing the composite layer (15) to form uniformly when solder is applied. This preliminary preparation simplifies the overall manufacturing process despite the multi-layer structure, as it provides a clear sequence of operations.
Solution Approach 2:
The composite layer (15) acts as an intermediary between the nickel layer (11) and the solder layer (13). It mediates the bonding process by providing a transition zone that combines characteristics of both materials, facilitating reliable joining while managing thermal stress. This intermediary layer simplifies the interface management between dissimilar materials.
3Strength
If the nickel layer is made thicker to improve bonding strength, then the mechanical strength increases, but the thermal conductivity to the heat dissipating member decreases
Solution Approach 1:
Different layers are assigned different thicknesses and material compositions based on their local functions: the nickel layer (11) is relatively thin and provides mechanical strength, while the composite layer (15) contains dispersed nickel particles that provide localized reinforcement without forming a continuous thick barrier. This local quality approach ensures heat can conduct through the structure while maintaining necessary mechanical strength at critical interfaces.
Solution Approach 2:
The composite layer (15) uses a dispersed mixture of nickel particles in solder matrix, creating a material that has both the mechanical strength properties of nickel and the thermal conductivity of solder. This composite material resolves the contradiction by providing strength where needed (at interfaces) while maintaining thermal pathways through the bulk material.
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 configuration enhances the mechanical strength and thermal shock resistance of the joint body, maintaining high bonding strength and durability even under extreme temperature conditions.
Implementation Method 1
The nickel in the composite layer extends from the nickel layer in the thickness direction and forms protrusions and recesses
Implementation Method 2
a joint body formed by joining an aluminum metal member (heat dissipating member) to a ceramic substrate is used as a wiring board
Implementation Method 3
The metal joint layer includes a nickel layer, a solder layer, and a composite layer containing a mix of nickel and solder
Data Source
AI summary
A joint body of the present disclosure includes a substrate including a base member having insulating properties and a metal layer positioned on a first main surface of the base member, a metal joint layer, and a metal member. The metal joint layer is positioned between the metal layer and the metal member of the substrate. The metal joint layer includes a nickel layer, a solder layer, and a composite layer containing a mix of nickel and solder. The nickel layer, the composite layer, and the solder layer are positioned in this order from the metal layer side to the metal member side. The nickel in the composite layer extends from the nickel layer in the thickness direction and forms protrusions and recesses.