IR Laser Soldering for LED Chip Mounting to Prevent Light Absorption
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Solution Overview
Problem
The existing light emitting elements experience reduced luminous efficiency due to solder being squeezed out from the mounting area, leading to light absorption and non-uniform heating causing voids and reliability issues in electrical conductivity.
Innovation Solution
The use of an IR laser to melt and form solder portions within the mounting area of the LED chip on the substrate, minimizing solder escape and ensuring uniform heating for stable bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If solder is applied to an area equal to or greater than the bottom area of the LED chip to ensure uniform distribution, then the solder coverage is improved, but the solder escapes from the mounting area and absorbs light, reducing luminous efficiency
Solution Approach 1:
The solder application process is segmented into two distinct stages: first applying solder to a limited area smaller than the LED chip bottom area, then applying additional solder to cover the remaining area. This segmentation allows precise control over solder placement, preventing overflow while ensuring complete coverage and uniform distribution.
Solution Approach 2:
The first solder is applied preliminarily to a restricted area before the LED chip is mounted. This preliminary action establishes a controlled foundation that prevents excessive solder from escaping during the subsequent mounting process, while still providing adequate bonding material in critical areas.
2Reliability
If reflow soldering is used to mount the LED chip, then the solder bonding is achieved, but non-uniform heat application causes voids that deteriorate electrical conductivity and reliability
Solution Approach 1:
The soldering method transitions from conventional reflow soldering with non-uniform heat distribution to laser soldering with highly controllable and uniform heat application. This parameter change in the heating process eliminates the formation of voids while maintaining reliable solder bonding, as the laser provides precise thermal control throughout the solder reflow process.
3Area of stationary object
If solder is applied to ensure complete coverage, then the bonding area is maximized, but the solder covers lateral sides of the LED chip and absorbs emitted light
Solution Approach 1:
The solder application approach changes from a single-layer thick application that flows laterally onto the LED chip sides to a controlled thin-layer application confined to the mounting area. This dimensional control ensures complete area coverage for bonding while preventing lateral overflow that would interfere with light emission.
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 luminous efficiency by preventing solder escape, reducing light absorption, and improving electrical conductivity and reliability by minimizing void formation.
Implementation Method 1
heating a solder material to its melting point or above with an IR laser
Implementation Method 2
heating a solder material to its melting point or above with an IR laser
Implementation Method 3
completely melting the solder material with an IR laser and curing the molten solder material
Data Source
AI summary
A light emitting element is disclosed. The light emitting element includes: an LED chip including a light emitting semiconductor stack and first and second electrode pads disposed under the light emitting semiconductor stack and spaced apart from each other; a substrate mounted with the LED chip and including a first electrode corresponding to the first electrode pad and a second electrode corresponding to the second electrode pad; a first solder portion connecting the first electrode pad and the first electrode; and a second solder portion connecting the second electrode pad and the second electrode. The first solder portion and the second solder portion are formed without escaping from the mounting area of the LED chip on the substrate by heating a solder material to its melting point or above with an IR laser.