Underfill Gap Filling Without Fillet for Light Extraction
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Solution Overview
Problem
Conventional underfill techniques for light emitting chips result in a fillet of underfill material extending outside the gap over the sidewalls, which interferes with light extraction and post-underfill processing such as encapsulation and optical coating applications.
Innovation Solution
The underfill material is configured to substantially fill the gap between the light emitting chip and the support surface without forming a fillet outside the gap over the sidewalls, providing mechanical support and thermal conduction while allowing for unobstructed light extraction and post-processing operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional underfill techniques are used to provide mechanical support and thermal conduction, then the underfill material fills the gap between chip and support, but a fillet extends outside the gap over sidewalls interfering with light extraction and post-processing
Solution Approach 1:
The harmful fillet portion of the underfill material is extracted/removed from the final structure. The underfill is applied to fill the gap but is then trimmed or controlled to eliminate the fillet that extends over the sidewalls, removing the source of light extraction interference while preserving the gap-filling function for mechanical support and thermal conduction
Solution Approach 2:
The underfill material is distributed non-uniformly: it is present within the gap area to provide mechanical support and thermal conduction, but deliberately absent from the sidewall regions where it would interfere with light extraction. This creates different material presence zones with different functional requirements
2Strength
If underfill material is applied to fill the gap between chip and support, then mechanical support is enhanced, but post-underfill processing such as encapsulation and optical coating becomes difficult
Solution Approach 1:
The underfill fillet that obstructs post-processing operations is removed. By eliminating the material extending over the sidewalls, subsequent processes such as encapsulation and optical coating can be applied directly to the chip sidewalls without obstruction, significantly improving ease of manufacture
Solution Approach 2:
The underfill is applied in a controlled manner from the beginning, with the gap-filling function performed but the harmful fillet formation prevented or removed before subsequent processing steps. This preliminary control of underfill geometry eliminates the need for complex post-processing workarounds
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 enhances light extraction and facilitates post-underfill processing by eliminating the interference caused by the fillet, ensuring effective mechanical support and thermal conduction without compromising the structural integrity or optical performance.
Implementation Method 1
provides at least one of (i) mechanical support for the light emitting chip and (ii) a thermal conduction path from the light emitting chip to the support surface
Data Source
AI summary
A light emitting chip is disposed on a support surface. A plurality of bonding bumps are disposed in a gap between the light emitting chip and the support surface. The plurality of bonding bumps provide at least one electrical power input path to the light emitting chip. An underfill comprising underfill material is disposed in the gap between the light emitting chip and the support surface such that the underfill substantially fills the gap but does not form a fillet extending outside the gap over sidewalls of the light emitting chip. The underfill is configured to provide at least one of (i) mechanical support for the light emitting chip and (ii) a thermal conduction path from the light emitting chip to the support surface.