Epi-Down Semiconductor Laser Mounting with Solder Relief Posts
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Solution Overview
Problem
Conventional epi-up semiconductor laser mounting configurations face inefficiencies in heat dissipation due to high thermal resistance, while epi-down configurations often result in solder-related issues such as shorting and blocking of light emission.
Innovation Solution
The introduction of posts on the semiconductor laser chip, evenly spaced and aligned with the laser ridge, provides a solder relief path and mechanical stability, preventing solder interference with the chip's facets and sidewalls during epi-down mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epi-up mounting configuration is used, then the substrate provides mechanical support, but heat dissipation efficiency deteriorates due to high thermal resistance
Solution Approach 1:
The patent inverts the conventional epi-up mounting configuration to epi-down mounting, where the epitaxial side with the active region is positioned directly on the heat sink instead of the substrate side. This inversion places the heat-generating active region in direct thermal contact with the heat sink, dramatically improving heat dissipation efficiency while the substrate remains attached to the back of the chip for mechanical support.
2Loss of energy
If epi-down mounting configuration is used, then heat dissipation efficiency improves, but solder-related issues such as shorting and blocking of light emission worsen
Solution Approach 1:
The patent introduces a solder resist layer as an intermediary material applied to the epitaxial side of the semiconductor chip. This layer prevents molten solder from flowing onto and shorting the electrical contacts or blocking the light-emitting facet during the epi-down mounting process, while allowing the active region to maintain direct thermal contact with the heat sink for efficient heat dissipation.
3Loss of energy
If heat sink is positioned close to epitaxial surface, then heat dissipation improves, but mechanical stability deteriorates
Solution Approach 1:
The patent inverts the mounting configuration so that the epitaxial side with the active region contacts the heat sink directly for optimal heat dissipation, while the substrate remains attached to the back of the chip to provide mechanical stability and structural support, thus resolving both thermal and mechanical requirements simultaneously.
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 enhances heat dissipation and mechanical stability, achieving high yields and improved thermal resistance, with reduced instances of solder-related failures and increased output power.
Implementation Method 1
heat dissipation from Joule heating becomes an overriding concern since, generally, the laser efficiency decreases substantially as the temperature of the active region increases. It is therefore beneficial to position a heat sink comprising a material with relatively high thermal conductivity
Implementation Method 2
heat will diffuse (primarily vertically, but also to some extent laterally for narrow ridges) toward and into the electroplated layer 107
Implementation Method 3
The laser apparatus is typically secured to the heat sink by means of indium or gold-tin alloy solders which form a thermal bond between the laser and the heat sink
Data Source
AI summary
A laser apparatus configured for epitaxial-side-down mounting on a heat sink. The laser apparatus includes a semiconductor laser structure and at least one post on a substrate where the laser structure and post are separated from each other by a channel. The laser structure and the posts optionally are coated with a heat-spreading material layer and are configured so that the maximum height of the posts is about the same as the maximum height of the laser structure. When the laser apparatus is mounted to a heat sink in an epi-down configuration using solder applied to the top of the laser structure and the at least one post, the channels between the at least one post and the laser structure provide a relief flow path for the solder and ensure that the laser structure does not come directly into contact with the solder.