Sequential TLP Bonding for Close-Spaced Semiconductor Lasers
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Solution Overview
Problem
Conventional semiconductor packaging processes face challenges in minimizing the spacing between semiconductor chips due to thermal interference and inflexible spacing constraints, leading to increased cost and size of optical systems.
Innovation Solution
A sequential bonding process using transient liquid phase bonding with selective activation, where a gold layer on semiconductor chips intermixes with AuSn pads on a substrate, allowing for reduced spacing without thermal interference by controlling temperature and time durations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional semiconductor packaging processes are used with submounts, then mechanical support and electrical connection are provided, but the spacing between lasers increases due to physical constraints of submounts
Solution Approach 1:
The patent extracts the bonding function from the mechanical support structure by directly bonding semiconductor lasers to the PIC substrate without intermediate submounts. This eliminates the submount's physical constraints that forced larger spacing between lasers, while maintaining reliable mechanical support and electrical connection through direct bonding interfaces.
Solution Approach 2:
The patent employs asymmetric thermal management by providing active cooling only at specific laser locations rather than uniform cooling across the entire substrate. This asymmetric approach allows closer spacing between lasers by locally managing thermal interference only where needed, rather than being constrained by uniform thermal fields across large submount areas.
2Temperature
If multiple semiconductor lasers are mounted onto one single submount, then spacing between lasers increases to avoid thermal interference, but this imposes design constraints and increases PIC chip size
Solution Approach 1:
The patent applies local quality by providing cooling specifically at laser locations rather than uniformly across the entire PIC substrate. This localized thermal management allows lasers to be placed closer together because each laser's thermal field is independently managed, eliminating the need for large uniform spacing that would be required with conventional submount-based approaches.
Solution Approach 2:
The patent segments the thermal management system into independent cooling zones at each laser location. By dividing the thermal control function into discrete local units rather than a single uniform system, the design can accommodate closer laser spacing while maintaining thermal stability at each individual laser site.
3Adaptability or versatility
If sequential laser mounting is performed, then manufacturing flexibility is reduced due to thermal interference, but closer spacing is desired to reduce system size and cost
Solution Approach 1:
The patent applies preliminary action by pre-cooling the PIC substrate before each laser bonding operation. This preparatory cooling step ensures that the substrate is ready to receive the next laser without residual thermal effects from previous bonding operations, enabling closer spacing while maintaining manufacturing flexibility through a standardized sequential process.
Solution Approach 2:
The patent employs periodic action through repeated cycles of substrate cooling followed by laser bonding. This periodic thermal management allows multiple lasers to be mounted in sequence at close spacing, as each bonding cycle is separated by a cooling period that resets the thermal state, enabling both close spacing and manufacturing flexibility.
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 method enables closer chip spacing while maintaining thermal stability, reducing system size and cost by minimizing thermal interference and improving manufacturing flexibility.
Implementation Method 1
bonding the first semiconductor chip and causing intermixing of the gold layer on the first semiconductor chip and the AuSn pad
Implementation Method 2
_transient liquid phase bonding process_
Implementation Method 3
_transient liquid phase bonding process_
Data Source
AI summary
Embodiments of the present disclosure include method for sequentially mounting multiple semiconductor devices onto a substrate having a composite metal structure on both the semiconductor devices and the substrate for improved process tolerance and reduced device distances without thermal interference. The mounting process causes “selective” intermixing between the metal layers on the devices and the substrate and increases the melting point of the resulting alloy materials.