Mounting Substrate Wiring Patterns with Edge Holes for LED Thermal Stress
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Light emitting devices with ceramic packages face issues of cracking and reduced heat dissipation due to thermal stress caused by differences in linear expansion coefficients between ceramic and mounting substrates, particularly when using solder or other joining members.
Innovation Solution
A mounting substrate design featuring wiring patterns with rectangular mounting portions and holes at the outer edges, allowing solder to spread laterally and increase the surface area subjected to thermal stress, thereby dispersing stress and enhancing heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an NSMD structure is employed to strengthen the joint, then the joint strength is improved, but the wire width of the wiring layer is narrowed and heat dissipation decreases
Solution Approach 1:
The pad structure is segmented into multiple regions: a central mounting portion for electrical connection and lateral surfaces for solder adhesion. This segmentation allows the wiring layer to maintain adequate width for heat dissipation while providing distributed bonding areas that strengthen the joint without requiring the entire pad area to be narrowed.
Solution Approach 2:
The joining member is extended from bonding only on the upper surface of the pad to also bonding on the lateral surfaces of the pad. This dimensional extension provides additional bonding area that strengthens the joint without reducing the planar width of the wiring layer, thereby maintaining heat dissipation capability.
2Strength
If an NSMD structure is employed to strengthen the joint, then the joint strength is improved, but the wiring layer surface area is reduced and reliability decreases
Solution Approach 1:
The pad is segmented into a mounting portion and lateral surfaces, allowing the wiring layer to maintain its full width for reliability while the segmented lateral surfaces provide additional bonding areas for the joining member, distributing stress and preventing breakage.
3Power
If a ceramic package with high thermal conductivity is used to supply large current, then the light emission output is improved, but thermal stress causes cracking in the joining member
Solution Approach 1:
Different regions of the pad are given different functions: the central mounting portion provides electrical connection and current flow path, while the lateral surfaces provide thermal stress relief through additional bonding. This local differentiation allows the system to handle high power while distributing thermal stress away from critical bonding points.
Solution Approach 2:
The joining member is extended to bond on lateral surfaces of the pad, creating a three-dimensional bonding structure. This additional dimensional bonding provides extra pathways for stress distribution, reducing the concentration of thermal stress at any single point and preventing cracking under high power conditions.
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 design stabilizes the mounting of electronic parts by reducing the risk of solder cracking and improving heat dissipation, even under high current conditions, while maintaining electrical connectivity and positioning accuracy.
Implementation Method 1
allowing the joining member to work its way into the lateral surfaces of the pad
Implementation Method 2
thermal stress produced by the difference in the coefficient of linear expansion between the ceramic and the mounting substrate
Data Source
AI summary
A mounting substrate includes: a base; and at least one pair of wiring patterns disposed apart from each other on the base. At least one of the wiring patterns has a mounting portion, which is configured to support an electronic part thereon and which is rectangular in a plan view. The at least one of the wiring patterns defines a hole, which exposes a part of the base and which is disposed in at least a part of an outer edge of the mounting portion.