VCSEL Bonding Dummy Posts for AR Coating Protection
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Solution Overview
Problem
The challenge in bonding vertical cavity surface emitting laser (VCSEL) devices is the potential damage to the anti-reflection coating during thermo-compression bonding due to direct contact with the bonding head, leading to uneven thermal transfer, bonding uniformity issues, and excessive strain on the VCSEL chip.
Innovation Solution
Incorporation of dummy posts extending outward from the anti-reflection coating, which serve as points of contact for the bonding head, preventing direct contact with the AR coating and ensuring uniform distribution of pressure and heat, thereby protecting the AR coating and enhancing bonding uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the bonding head directly contacts the anti-reflection coating during thermo-compression bonding, then bonding can be performed, but the AR coating is damaged and thermal transfer is uneven
Solution Approach 1:
Dummy posts are introduced as intermediary structures between the bonding head and the AR coating. These posts extend through the substrate and provide contact points for the bonding head, preventing direct contact with the AR coating while enabling force and heat transfer during the bonding process.
Solution Approach 2:
The bonding interface is segmented by introducing discrete dummy posts at specific locations rather than requiring uniform contact across the entire AR coating area. This segmentation allows the bonding head to contact only the dummy posts, protecting the AR coating while providing sufficient contact points for bonding.
2Ease of manufacture
If the bonding head directly contacts the substrate surface, then bonding can be performed, but pressure and heat are unevenly distributed
Solution Approach 1:
The dummy posts serve as mediators that concentrate and uniformly distribute the bonding head's pressure and heat to the interconnects. By channeling the bonding forces through these specifically positioned posts, the system achieves more uniform thermal and mechanical transfer compared to direct substrate contact.
3Reliability
If the AR coating is protected from bonding head contact, then coating integrity is maintained, but bonding force transfer may be insufficient
Solution Approach 1:
The force transfer path is extended into the third dimension by incorporating dummy posts that protrude through the substrate thickness. This vertical dimension provides dedicated force transfer pathways that are decoupled from the AR coating plane, ensuring sufficient bonding force transfer while maintaining coating protection.
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 dummy posts allow for centered bonding over interconnects without damaging the AR coating, ensuring uniform thermal and force transfer, reducing stress on the VCSEL device, and improving bonding yield.
Implementation Method 1
ensuring uniform distribution of pressure and heat
Implementation Method 2
ensuring uniform distribution of pressure and heat
Data Source
AI summary
In some implementations, a VCSEL device includes a substrate having a first surface and a second surface opposite the first surface. The VCSEL device may include a VCSEL array including a plurality of VCSELs disposed on the first surface of the substrate. The plurality of VCSELs may be configured for backside emission through the substrate. Respective emission areas for the plurality of VCSELs may be defined on the second surface of the substrate. The respective emission areas may define a perimeter of an emission region of the VCSEL device. The VCSEL device may include an anti-reflection (AR) coating on the second surface of the substrate. The VCSEL device may include a plurality of dummy posts disposed on the AR coating. The plurality of dummy posts may be positioned within the emission region, outside of the respective emission areas for the plurality of VCSELs.