LED Substrate Indentations for Thermal Stress Relief
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Solution Overview
Problem
High-power LEDs and semiconductor devices experience thermal stress due to differing coefficients of thermal expansion and temperature gradients, leading to solder connection cracks and reliability issues, particularly in automotive applications where harsh thermal shock tests are required.
Innovation Solution
Incorporating longitudinal indentations or grooves in the substrate or heatsink bottom surface to alleviate thermal stress, allowing for even stress distribution and preventing solder connection cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high-power LEDs are used to increase luminance and energy efficiency, then lighting performance is improved, but thermal stress increases leading to solder connection cracks
Solution Approach 1:
The substrate is designed with non-uniform thickness, creating regions of varying thermal mass and stress distribution. Thinner regions allow for greater flexibility and stress relief, while thicker regions provide structural support, enabling the substrate to accommodate thermal expansion differences without cracking solder connections.
Solution Approach 2:
The substrate incorporates indentations or cavities that segment the continuous structure into distinct regions. These segmented areas create stress relief zones that prevent the propagation of thermal stress through the entire substrate, thereby protecting solder connections from crack formation while maintaining overall structural integrity.
2Strength
If substrate thickness is increased to improve structural strength, then mechanical strength is improved, but thermal stress concentration increases
Solution Approach 1:
The substrate employs variable thickness design where different regions have different thicknesses optimized for their specific functions. Areas requiring high strength maintain greater thickness, while regions prone to stress concentration are thinned to reduce thermal stress accumulation, achieving both strength and stress relief.
Solution Approach 2:
The substrate incorporates curved surfaces and rounded transitions instead of sharp angles or abrupt thickness changes. These curved geometries distribute thermal stress more evenly throughout the structure, preventing stress concentration at sharp corners or sudden thickness transitions while maintaining overall structural strength.
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
Enhances the reliability of semiconductor modules by reducing thermal stress and preventing cracks, enabling them to pass stringent thermal shock tests.
Implementation Method 1
High-power LEDs and semiconductor devices experience thermal stress due to differing coefficients of thermal expansion and temperature gradients
Data Source
AI summary
Light-emitting diode (LED) devices are described herein. An LED device includes a substrate. The substrate has a top surface and a bottom surface opposite the top surface. The bottom surface has at least one indentation that runs lengthwise across at least a portion of the substrate. The LED device also includes a semiconductor surface mounted device (SMD) over the top surface of the substrate.