Laser Diode Package Exothermic Soldering Assembly
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Solution Overview
Problem
The attachment of semiconductor laser diodes to heat sinks is hindered by thermal expansion mismatch issues, leading to degraded performance and reduced service life due to warpage or fracturing during heating and cooling cycles, especially when using conventional soldering methods with different coefficients of thermal expansion (CTE) materials.
Innovation Solution
A novel laser diode package design incorporating an exothermic layer between the bar solder layer and the heat-sinking solder layer, which is activated by an internal energy source to propagate an exothermic reaction, melting and solidifying the solder layers without significantly heating or cooling the laser diode or heat sink, thus minimizing CTE mismatch problems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional soldering is used to attach laser diodes to heat sinks, then electrical and thermal connection is achieved, but warpage or fracturing occurs due to CTE mismatch during heating and cooling cycles
Solution Approach 1:
The invention changes the temperature parameter during assembly by using exothermic reaction to melt solder locally without heating the entire assembly. This avoids the thermal expansion and contraction that causes warpage and fracturing in conventional soldering, while still achieving proper solder flow and joint formation.
Solution Approach 2:
The invention replaces the conventional external heating system with an internal chemical energy source (exothermic reaction). This substitution eliminates the thermal stress cycle that causes mechanical failure, while still providing the necessary heat for solder melting and bonding.
2Stability of the object's composition
If hard solder is used on low thermally conductive heat sink, then CTE mismatch is reduced, but laser diode operates at higher temperature reducing service life
Solution Approach 1:
The invention segments the heat sink into different material zones: a low CTE material (ceramic or composite) in contact with the laser diode bar to minimize thermal stress, and a high thermal conductivity material (metal) in the heat dissipation pathways. This segmentation allows simultaneous optimization of both CTE matching and thermal management.
3Temperature
If soft solder is used on high thermally conductive heat sink, then thermal management is improved, but electrical and thermal migration of solder occurs under operating conditions
Solution Approach 1:
The invention uses composite solder materials or layered solder structures that combine the benefits of soft solder (low melting point for easy processing) with the stability of hard solder (resistance to migration). The composite structure allows controlled melting during assembly while maintaining structural integrity and resistance to thermal and electrical migration during operation.
4Ease of manufacture
If external heating is applied to melt solder in conventional soldering, then solder layers are melted for attachment, but excessive heat is transferred to laser diode and heat sink causing thermal expansion and contraction
Solution Approach 1:
The invention introduces an intermediary exothermic layer between the external energy source and the solder joints. This intermediary confines the thermal energy generation to the immediate vicinity of the solder layers, providing sufficient heat for melting while acting as a thermal barrier that prevents excessive heat transfer to the laser diode and heat sink, thereby minimizing thermal expansion and contraction.
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 minimizes thermal expansion issues during assembly, reducing the risk of warpage and fracturing, and enhances the service life of high-powered laser diodes by maintaining stable temperatures and mechanical integrity.
Implementation Method 1
the exothermic layer is exposed to a known energy source which causes an exothermic reaction to propagate through the exothermic layer thereby melting at least a portion of the bar and heat-sinking solder layers
Implementation Method 2
melting at least a portion of the bar and heat-sinking solder layers, which subsequently solidify
Implementation Method 3
melting at least a portion of the bar and heat-sinking solder layers, which subsequently solidify
Data Source
AI summary
A laser diode package according to the present invention is composed of CTE mismatched components soldered together. The laser diode package includes a laser diode bar, at least one heat sink, and at least one exothermic layer. Solder layers are adjacent the heat sink(s) and laser diode bar, respectively. The exothermic layer(s) are positioned between the solder layers. The exothermic layer(s) are exposed to an energy source which causes an exothermic reaction to propagate through the exothermic layer thereby melting the solder layers and solder layers. The exothermic layer(s) may be designed to provide sufficient heat to melt the solder layers and solder layers but provide only minimal heat to the laser diode bar and heat sink(s). Several packages can be stacked together to form a laser diode array.