Liquid Cooled Laser Bar Arrays With Diamond Copper Spacers
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Solution Overview
Problem
Laser diode arrays face reliability issues due to thermal stress and inefficiencies in heat removal, particularly in harsh environments, as existing technologies like microchannel and macrochannel coolers are prone to leaks, misalignment, and thermal expansion mismatches, leading to reduced performance and lifespan.
Innovation Solution
A liquid-cooled laser diode array using copper/diamond composite spacers with matched thermal expansion to the laser bars, allowing for hard soldering and mounting on an electrically isolating ceramic substrate, with a macrochannel cooler for enhanced heat dissipation and mechanical robustness, eliminating the need for de-ionized water and o-ring seals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If microchannel coolers are used for heat removal, then heat dissipation capability is improved, but device complexity increases and reliability decreases due to leaks and misalignment
Solution Approach 1:
The patent extracts the coolant channels from the ceramic substrate and relocates them to the copper heat sink. This eliminates the need for sealing the channels within the ceramic structure, removing the source of leaks and misalignment issues while maintaining effective heat removal from the laser diode bars.
Solution Approach 2:
The copper heat sink acts as an intermediary between the laser diode bars and the coolant. It receives heat from the lasers and transfers it to the coolant channels, decoupling the thermal management function from the structural ceramic substrate and enabling more reliable assembly.
2Strength
If hard solders are used for assembly, then mechanical strength is improved, but thermal expansion stress increases due to material mismatches
Solution Approach 1:
The patent employs a composite assembly structure where the copper heat sink is mechanically coupled to the ceramic substrate. This composite design allows each material to perform its optimal function (copper for thermal conduction, ceramic for electrical insulation) while the mechanical coupling accommodates thermal expansion differences, enabling the use of strong hard solders without excessive stress.
Solution Approach 2:
The invention changes the thermal expansion parameter matching by using copper (which has higher thermal expansion) in contact with the laser bars, and allowing the ceramic substrate to be mechanically coupled rather than soldered. This parameter optimization reduces thermal stress in the critical laser bar joints while maintaining overall assembly strength.
3Temperature
If de-ionized water is used for cooling, then cooling efficiency is improved, but corrosion resistance decreases requiring additional protective measures
Solution Approach 1:
The copper heat sink serves as an intermediary barrier between the de-ionized water coolant and the ceramic substrate/laser assembly. This intermediate layer protects the sensitive components from direct exposure to corrosive coolant, allowing the use of efficient de-ionized water cooling without compromising component longevity.
4Power
If laser diode bars are mounted close together, then power density is improved, but heat removal difficulty increases
Solution Approach 1:
The patent merges multiple heat removal functions into a single copper heat sink structure that contacts the back of all laser diode bars simultaneously. This unified thermal management system efficiently collects heat from closely spaced lasers and transfers it to the coolant, enabling high power density operation without compromising heat removal capability.
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 solution provides improved heat removal and reliability, enabling high-powered continuous wave and pulsed laser operations with reduced thermal stress and increased mechanical robustness, surpassing the limitations of previous cooling methods.
Implementation Method 1
the materials used must also have high electrical conductivity and thermal conductivity
Implementation Method 2
the materials used must also have high electrical conductivity and thermal conductivity. Historically, this has required the use of materials that have different thermal expansion properties
Implementation Method 3
macrochannel cooler for enhanced heat dissipation
Data Source
Figure 1~1A
Figure 2~2A
AI summary
A laser diode array (12) having a plurality of laser diode bars (16) bonded by a hard solder to expansion matched spacers (14) and mounted on a gas or liquid cooled heatsink (30). The spacers (14) are formed of a material such as copper/diamond composite material having a thermal expansion that closely matches that of the laser bars (16).