Flip-Chip LED Gap Engineering for Encapsulant Intrusion Prevention
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Solution Overview
Problem
Existing semiconductor light emitting diodes (LEDs) face challenges in maintaining operational efficiency due to encapsulant intrusion into the gap between the LED contacts and substrate pads, which can degrade the device's performance during encapsulation and curing processes.
Innovation Solution
A geometric configuration of the gap and the use of a filler material, such as a silicone-based or solder stop material, to prevent encapsulant intrusion, ensuring a reliable die attach and maintaining device efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gap between LED contacts and substrate pads is reduced to improve electrical connection, then electrical conductivity is improved, but encapsulant intrusion into the gap increases which degrades device performance
Solution Approach 1:
A barrier layer is introduced as an intermediary element between the LED contact and the substrate pad, filling the gap between them. This barrier layer prevents encapsulant from intruding into the gap while maintaining electrical connectivity through conductive material, thus resolving the contradiction between improving electrical connection and preventing encapsulant intrusion.
2Object-affected harmful factors
If the gap dimensions are increased to prevent encapsulant intrusion, then encapsulant intrusion is reduced, but electrical connection quality deteriorates
Solution Approach 1:
The barrier layer is constructed from composite material comprising conductive material and non-conductive material. The conductive material ensures electrical connectivity while the non-conductive material prevents encapsulant intrusion, allowing the gap to be sufficiently large to prevent intrusion while maintaining electrical connection quality.
3Ease of manufacture
If encapsulant is allowed to enter the gap during curing to ensure complete encapsulation, then encapsulation completeness is improved, but device operation is degraded due to encapsulant in the gap
Solution Approach 1:
The barrier layer is pre-installed in the gap before the encapsulation process. This preliminary action prevents encapsulant from entering the gap during curing, eliminating the need for post-processing removal steps and ensuring device operation is not degraded while maintaining encapsulation completeness.
4Ease of manufacture
If the barrier layer is made thinner to maintain gap visibility and access, then manufacturing access is improved, but protection against encapsulant intrusion is reduced
Solution Approach 1:
The barrier layer parameters are optimized by controlling its thickness within a specific range (0.5-5.0 micrometers) and adjusting the ratio of conductive to non-conductive material. This parameter optimization maintains sufficient protection against encapsulant intrusion while keeping the barrier layer thin enough to allow manufacturing access and visibility.
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 solution effectively prevents encapsulant intrusion, maintaining the die shear strength and operational reliability of flip-chip mounted LEDs by controlling the gap dimensions and using appropriate filler materials, thus ensuring consistent performance.
Implementation Method 1
the encapsulant expands during heating thereof, for example during curing thereof
Data Source
AI summary
A horizontal LED die is flip-chip mounted on a mounting substrate to define a gap that extends between the closely spaced apart anode and cathode contacts of the LED die, and between the closely spaced apart anode and cathode pads of the substrate. An encapsulant is provided on the light emitting diode die and the mounting substrate. The gap is configured to prevent sufficient encapsulant from entering the gap that would degrade operation of the LED.