VCSEL Emitter Assembly Locking Pillars for Fine-Pitch Reflow Alignment
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Solution Overview
Problem
The existing methods for bonding vertical cavity surface emitting lasers (VCSELs) to integrated circuit driver chips face challenges with misalignment due to vibration during solder mass reflow, especially at fine pitches, leading to high complexity, cost, and low throughput in mass production.
Innovation Solution
The use of a VCSEL chip in a flip chip configuration with a carrier and conductive pillars, along with dummy pillars that are electrically isolated, minimizes misalignment by mating with slots, enabling the use of solder mass reflow for bonding, thus reducing complexity and increasing throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If solder mass reflow is used for bonding VCSELs to driver chips, then throughput and cost are improved, but misalignment occurs due to vibration during the process
Solution Approach 1:
The patent applies preliminary action by pre-forming dummy pillars on one component and corresponding slots on the other component before the bonding process. These alignment features are created in advance to guide and constrain the relative positioning of the VCSEL chip and driver chip during solder reflow, preventing misalignment caused by vibration while maintaining the benefits of mass reflow bonding.
2Manufacturing precision
If thermal compression bonding is used to avoid misalignment, then alignment precision is improved, but device complexity and process complexity increase
Solution Approach 1:
The patent introduces dummy pillars and slots as intermediary alignment features that mediate between the two components during bonding. These intermediaries provide mechanical guidance and constraint, enabling the use of simpler solder reflow processes while achieving alignment precision previously only attainable through complex thermal compression bonding processes.
3Manufacturing precision
If dummy pillars with slots are added to the emitter assembly, then alignment during solder reflow is improved, but device complexity increases
Solution Approach 1:
The dummy pillars serve as disposable alignment features that are non-functional during VCSEL operation. They are sacrificial elements used only during the bonding process to ensure proper alignment, then they remain as inert structural features. This approach adds minimal complexity to the functional VCSEL array while solving the alignment problem.
4Quantity of substance
If fine pitch VCSEL arrays are bonded using conventional methods, then VCSEL density is improved, but misalignment and bonding failures increase
Solution Approach 1:
The patent applies segmentation by dividing the alignment function from the bonding function. The dummy pillars and slots provide dedicated alignment guidance, while the conductive pillars handle the electrical and mechanical bonding. This separation allows fine pitch VCSEL arrays to be bonded reliably, as each feature type is optimized for its specific function without interference from the other.
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 allows for efficient and cost-effective mass production of VCSEL arrays with fine pitches by stabilizing the VCSEL chip during solder reflow, improving alignment and reducing the complexity and cost associated with thermal compression bonding.
Implementation Method 1
a plurality of conductive pillars that electrically connect the plurality of first electrical contacts and the plurality of second electrical contacts
Implementation Method 2
performing a solder reflow procedure on the emitter assembly
Data Source
AI summary
In some implementations, an emitter assembly includes a vertical cavity surface emitting laser (VCSEL) chip including a plurality of VCSELs. The emitter assembly may include a plurality of conductive pillars electrically connected to the VCSEL chip. The emitter assembly may include a dummy pillar, electrically isolated from the VCSEL chip, mating with a slot. The VCSEL chip may include one of the dummy pillar or the slot.