Semiconductor Laser Welding with Focus Delocalization Compensation
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Solution Overview
Problem
Current laser welding technologies cannot effectively bond semiconductor materials with opaque materials, such as silicon and metal, due to the challenges of nonlinear interactions and delocalization of laser energy within semiconductor materials, which limits their application in microelectronics and other fields.
Innovation Solution
A method and system that utilize pulsed laser radiation to weld semiconductor workpieces by determining and compensating for the delocalization of the laser focus within the semiconductor material, ensuring the intensity maximum is positioned at the interface with the opaque workpiece, thereby achieving a strong and reliable bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the geometric focus is positioned at the exit surface of the semiconductor workpiece, then the laser beam can enter through the entrance surface and reach the interface, but the nonlinear interaction causes delocalization of the intensity maximum, preventing effective welding
Solution Approach 1:
The patent applies preliminary action by pre-determining the delocalization distance through test irradiations before the actual welding process. This advance measurement allows the system to compensate for nonlinear effects by adjusting the focus position upstream, ensuring the intensity maximum reaches the interface during welding.
Solution Approach 2:
The patent implements feedback by using a measuring unit to detect the actual position of the intensity maximum within the semiconductor material. This measured information is fed back to adjust the focus position, creating a closed-loop control system that compensates for delocalization and ensures reliable welding.
2Use of energy by moving object
If high-power ultrashort pulse lasers are used to deliver sufficient energy through the semiconductor, then the laser can penetrate the transparent material, but the Kerr-induced self-focusing and plasma absorption cause energy delocalization and saturation
Solution Approach 1:
The patent extracts the delocalization effect from the welding process by separately measuring it through test irradiations. By isolating and quantifying the delocalization distance, the system can compensate for it in the actual welding process, thereby maintaining energy deposition precision despite using high-power ultrashort pulses.
Solution Approach 2:
The patent applies parameter changes by adjusting the focus position based on the measured delocalization distance. This dynamic adjustment of the focus parameter compensates for the nonlinear propagation effects, ensuring that the intensity maximum is precisely positioned at the interface during welding.
3Strength
If the focus is positioned at the interface between workpieces, then optimal bonding should be achieved, but the delocalization of intensity maximum upstream prevents the intensity maximum from reaching the interface
Solution Approach 1:
The patent applies preliminary anti-action by positioning the geometric focus upstream of the interface to counteract the downstream shift caused by Kerr-induced self-focusing. This pre-compensation ensures that the intensity maximum, despite the nonlinear propagation, reaches the interface at the correct position for optimal bonding.
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 enables reliable, repeatable, and reproducible laser welding of semiconductor and opaque materials, optimizing bonding strength by maximizing energy absorption at the interface and compensating for nonlinear propagation effects.
Implementation Method 1
This uncommon material behavior mainly results from the competition between the Kerr-induced self-focusing effect on the one hand, and plasma absorption and defocusing effects on the other hand
Implementation Method 2
This uncommon material behavior mainly results from the competition between the Kerr-induced self-focusing effect on the one hand, and plasma absorption and defocusing effects on the other hand
Implementation Method 3
The energy of the laser beam thus melts material of the two workpieces, and the two workpieces are welded together
Data Source
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AI summary
The invention relates to a methodfor welding a first workpiece (11) to a second workpiece (12) by means of a laser. It is an object of the invention to provide a reliable, repeatable and reproducible approach for laser welding of two workpieces one of which consists of a semiconductor material. The method proposed by the invention comprises the following steps: Irradiating the first workpiece (11) with a beam of pulsed laser radiation, wherein the first workpiece (11) consists of a semiconductor material which is transparent at the wavelength of the laser radiation, so that the beam enters the first workpiece (11 ) through an entrance surface and leaves it through an exit surface, the geometric focus of the beam being positioned in the plane of the exit surface; determining a delocalization of the focus caused by nonlinear interaction of the laser radiation with the semiconductor material; placing the second workpiece (12) against the first workpiece (11); and, again, irradiating the first workpiece (11) with the laser beam of pulsed laser radiation, the focus of the laser radiation being positioned along the beam direction taking into account the determined delocalization so that the intensity maximum is located in the plane of the exit surface forming the interface of the two workpieces (11, 12), whereby the first workpiece (11) is welded to the second workpiece (12). Moreover, the invention relates to a System for welding a first workpiece (11) to a second workpiece (12).