Semiconductor Laser Au Plating Thickness Asymmetry
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Solution Overview
Problem
The existing semiconductor light-emitting devices with multiple laser elements on a shared substrate experience polarized light rotation due to asymmetrical residual stress from differing linear expansion coefficients between the laser elements and their packages, leading to unstable light injection efficiency in optical systems.
Innovation Solution
The semiconductor light-emitting device features a nonuniform average thickness of Au plating on semiconductor laser elements, with thinner plating on one area and thicker on the opposing area, to mitigate polarized light rotation by managing stress distribution during mounting on a package.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple semiconductor laser elements are formed on the same substrate and mounted on a package using solder, then the light output increases, but polarized light rotation occurs due to asymmetrical residual stress from linear expansion coefficient differences
Solution Approach 1:
The patent intentionally creates asymmetrical Au plating thickness distribution on the semiconductor laser element surfaces. By making the plating thickness non-uniform (thinner on one area, thicker on the opposing area), the design compensates for the asymmetrical residual stress caused by multiple laser elements on a shared substrate, thereby preventing polarized light rotation while maintaining high light output
Solution Approach 2:
The patent changes the physical parameter of Au plating thickness from uniform to non-uniform distribution. This parameter modification alters the stress distribution characteristics of the semiconductor laser elements, enabling compensation for asymmetrical residual stress and stabilization of polarized light characteristics during high-temperature mounting processes
2Ease of manufacture
If solder is used to mount semiconductor laser elements on a package, then the mounting temperature reaches 300°C or more, but residual stress remains at operating temperatures due to linear expansion coefficient differences
Solution Approach 1:
The patent addresses thermal expansion coefficient differences between materials (GaAs substrate, Au plating, solder, and package) by designing non-uniform Au plating thickness. This configuration allows the plating layer to compensate for differential thermal expansion and contraction during heating to 300°C and subsequent cooling, reducing residual stress at operating temperatures
Solution Approach 2:
The patent converts the potentially harmful effect of linear expansion coefficient differences into a beneficial stress compensation mechanism. By strategically designing non-uniform Au plating thickness, the natural thermal expansion and contraction of different materials during soldering are transformed into a self-compensating system that reduces residual stress rather than causing damage
3Stress or pressure
If a submount made of AlN is inserted between the package and semiconductor laser element, then residual stress is reduced, but it cannot be reduced to 0
Solution Approach 1:
The patent applies local quality modification by creating non-uniform Au plating thickness in specific areas of the semiconductor laser element surfaces. Instead of uniformly thickening or thinning the plating, the design targets specific regions to generate localized stress compensation, achieving complete residual stress elimination without adding structural complexity
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 approach effectively prevents polarized light rotation, ensuring stable light injection into optical systems by balancing stress across the light-emitting areas, thereby maintaining consistent light power delivery.
Implementation Method 1
residual stress remains at an operating temperature of 100° C. or below due to a difference in the linear expansion coefficient between the semiconductor laser element and the package
Data Source
AI summary
Semiconductor laser elements are formed on a common substrate. Au plating is formed on principal surfaces of the semiconductor laser elements. The semiconductor laser elements are mounted on a package with solder applied to the Au plating. Areas opposed to each other across a light-emitting area of each semiconductor laser element are designated first and second areas. Average thickness of the Au plating is different in the first and second areas of each semiconductor laser element.