Composite Substrate with Alternating Diamond and Metal Segments
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Solution Overview
Problem
Active electronic devices such as semiconductor lasers and laser diodes face challenges in heat removal due to thermal expansion mismatch between the device materials and submount substrates, leading to bonding failures and inefficient heat transfer, especially when using diamond substrates which have high thermal conductivity but low thermal expansion coefficients.
Innovation Solution
A composite substrate with an alternating pattern of diamond and metal portions, where diamond portions facilitate phonon transport for heat spreading and metal portions enable electron-based heat transport, allowing for tuned coefficient of thermal expansion (CTE) matching and enhanced heat removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If diamond substrate is used for heat removal, then thermal conductivity is improved, but coefficient of thermal expansion mismatch worsens
Solution Approach 1:
The patent employs a composite substrate structure combining diamond and metal portions. The diamond portions provide high thermal conductivity for efficient heat removal, while the metal portions have higher CTE values that match active devices better. This composite approach allows simultaneous optimization of both heat removal efficiency and bonding reliability by leveraging the complementary properties of different materials.
Solution Approach 2:
The substrate is designed with spatially varying properties through alternating diamond and metal portions. Diamond regions directly beneath heat-generating active devices provide localized high thermal conductivity, while metal regions provide CTE matching. This local quality differentiation allows each material to be positioned where its specific properties are most beneficial, resolving the contradiction between heat removal and bonding reliability.
2Reliability
If metal substrate is used for CTE matching, then bonding reliability is improved, but thermal conductivity deteriorates
Solution Approach 1:
The composite substrate combines metal and diamond portions, where metal regions provide CTE matching for bonding reliability while diamond regions provide high thermal conductivity. This composite structure overcomes the limitation of pure metal substrates by integrating the superior thermal properties of diamond in strategically positioned regions.
Solution Approach 2:
Diamond portions are positioned locally beneath active devices where heat generation occurs, providing localized high thermal conductivity. The metal portions are positioned in regions where CTE matching is critical for bonding. This spatial differentiation of material properties allows each material to optimize its specific function, resolving the contradiction between bonding reliability and heat removal efficiency.
3Reliability
If CTE matching is prioritized, then bonding reliability is improved, but heat removal efficiency deteriorates
Solution Approach 1:
The patent resolves this contradiction by creating a composite substrate where metal portions provide CTE matching for bonding reliability while diamond portions provide high thermal conductivity for heat removal. The composite structure allows both requirements to be satisfied simultaneously through the synergistic combination of materials with complementary properties.
Solution Approach 2:
The substrate is segmented into alternating diamond and metal portions rather than using a uniform material. This segmentation allows different regions to fulfill different functions: metal regions for CTE matching and bonding, diamond regions for heat removal. The segmented composite structure enables simultaneous optimization of bonding reliability and heat removal efficiency.
4Loss of energy
If diamond portions are increased for heat removal, then thermal conductivity is improved, but CTE mismatch worsens
Solution Approach 1:
Diamond portions are positioned locally beneath active devices where heat generation occurs, providing localized high thermal conductivity. The proportion and distribution of diamond versus metal portions are optimized so that heat removal is maximized where needed while CTE matching is maintained in regions where thermal expansion stresses develop. This spatial optimization resolves the contradiction between heat removal efficiency and thermal stress reduction.
Solution Approach 2:
The composite substrate combines diamond and metal in optimized proportions and patterns. The metal portions, with their higher CTE values, are positioned and sized to provide CTE matching that reduces thermal stress, while diamond portions provide heat removal. The composite structure allows simultaneous optimization of heat removal efficiency and thermal stress management through proper material distribution.
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 solution reduces thermal stress on active devices, enabling them to operate at higher power levels or for longer durations while minimizing temperature oscillations and maintaining efficient heat removal, thus extending device lifespan and performance.
Implementation Method 1
The diamond portions of the submount transport can spread heat energy via phonon transport along the lattice of diamond Sp3 carbon-carbon bonds
Implementation Method 2
the metal or metallic portions transport and spread heat energy via electron movement
Data Source
AI summary
A composite substrate includes a submount substrate of an alternating pattern of electrically insulative portions, pieces, layers or segments and electrically conductive portions, pieces, layers or segments, and a shaft, back or plate for supporting the alternating pattern of electrically insulative portions and electrically conductive portions. An active device having a P-N junction can be mounted on the submount substrate. The electrically insulative portions, pieces, layers or segments can be formed from diamond while the electrically conductive portions, pieces, layers or segments can be formed from a metal or metal alloy.