PCSEL Laser Focusing for Long Rayleigh Length Soldering
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Solution Overview
Problem
Existing laser soldering apparatuses face challenges in maintaining a high energy density across a wide range due to the short Rayleigh length of focused laser beams, which is insufficient for accurate soldering when the substrate warps or solder positions deviate from the normal height, as the beam waist position limits the irradiation area.
Innovation Solution
A laser irradiation method and apparatus utilizing a photonic crystal surface emitting laser element with a focusing lens for spatial propagation, allowing the laser beam to be focused and irradiated at any position within the Rayleigh length range, eliminating the need for a collimating lens and extending the Rayleigh length by maintaining a collimated beam with minimal divergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a focusing lens with a short focal length is used to reduce beam diameter and achieve high energy density, then the beam diameter is reduced and energy density is improved, but the Rayleigh length becomes short which limits the irradiation range
Solution Approach 1:
The patent changes the beam quality parameter by using a laser source that emits a beam with M²≈1 (close to diffraction limit), which fundamentally alters the relationship between focal length and Rayleigh length. This allows using short focal length lenses while maintaining long Rayleigh length because the beam divergence is minimized through superior beam quality control
Solution Approach 2:
The patent implements dynamic adjustment of the laser beam parameters (wavelength, power, pulse duration) to optimize both energy density and Rayleigh length for different soldering conditions. The system can adaptively change beam characteristics to maintain high energy density across varying working distances and substrate positions
2Use of energy by moving object
If the beam waist position is fixed, then the energy density is maximized at that position, but the irradiation area is limited and cannot accommodate position deviations
Solution Approach 1:
The patent employs dynamic focusing mechanisms that can adjust the beam waist position in real-time to track and compensate for substrate position deviations. This allows the system to maintain maximum energy density at the actual solder joint location even when it differs from the nominal position
Solution Approach 2:
The system uses feedback from position detection (optical sensors or vision systems) to continuously adjust the beam waist position and maintain optimal energy density. The feedback loop compensates for substrate warping and positioning errors by dynamically repositioning the focal point
3Length of moving object
If a collimating lens is added to extend the Rayleigh length, then the Rayleigh length is extended, but the device complexity increases
Solution Approach 1:
The patent extracts and eliminates the collimating lens from the optical system by using a laser source that inherently produces a collimated or near-collimated beam (M²≈1). This removes the need for additional optical components while maintaining the desired long Rayleigh length, thereby reducing system complexity
Solution Approach 2:
The laser source itself provides the collimation function that would otherwise require a separate collimating lens. The beam quality of the laser (M²≈1) enables it to self-collimate over long distances, making the system self-sufficient and reducing component requirements
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 ensures consistent high energy density across a wider range, enabling accurate soldering even when substrate positions deviate, as the extended Rayleigh length accommodates variations in height and reduces the need for complex optical systems.
Implementation Method 1
entering a laser beam emitted from a photonic crystal surface emitting laser element to a focusing lens by spatial propagation
Implementation Method 2
irradiating the laser beam focused by the focusing lens onto an object to be irradiated
Data Source
AI summary
A laser irradiation apparatus including: a photonic crystal surface emitting laser (PCSEL) element configured to emit a laser beam; a laser head configured to focus the laser beam emitted from the PCSEL element by a focusing lens thereof in an optical transmission path by spatial propagation; and a moving mechanism configured to irradiate the laser beam focused by the focusing lens onto an object to be irradiated with the laser beam at any irradiation position within a Rayleigh length range regardless of a beam waist position of the laser beam in an optical axis direction by a movement of the focusing lens relative to the object to be irradiated along the optical axis direction of the laser beam.