Bus Bar Terminal Laser Welding for Deep Penetration Without Sputtering
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Solution Overview
Problem
Existing laser welding methods for bus bars in power conversion devices face challenges with sputtering in keyhole mode welding and shallow penetration in thermal conduction mode welding, making it difficult to efficiently weld thick bus bars.
Innovation Solution
A laser welding method that involves irradiating the upper surfaces of overlapping bus bar terminals with a laser along their edges multiple times under thermal conduction mode conditions, ensuring deep penetration and suppressing sputtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If keyhole mode welding is used to achieve deep penetration, then penetration depth is improved, but sputtering occurs causing defects
Solution Approach 1:
The patent applies periodic action by performing laser irradiation multiple times (first irradiation, second irradiation, and optional third irradiation) rather than a single continuous exposure. This multi-stage periodic approach allows the weld pool to form and solidify in controlled intervals, suppressing sputtering while achieving the required penetration depth through cumulative thermal effect.
Solution Approach 2:
The welding process is segmented into distinct stages: first laser irradiation to create initial melting, second laser irradiation to achieve deep penetration, and optionally third irradiation to complete the weld. This segmentation of the welding action into multiple discrete steps allows control over the sputtering phenomenon while maintaining deep penetration capability.
2Object-generated harmful factors
If thermal conduction mode welding is used to suppress sputtering, then sputtering is reduced, but penetration depth becomes shallow
Solution Approach 1:
The patent uses periodic laser irradiation in multiple stages, where each irradiation cycle operates in thermal conduction mode to suppress sputtering, while the cumulative effect of repeated irradiation achieves the required penetration depth. This transforms a single shallow thermal conduction weld into a deep penetration weld through time-multiplexed thermal accumulation.
Solution Approach 2:
The patent maintains continuous useful action by performing multiple successive laser irradiations without interruption to the welding process. The thermal energy from each irradiation accumulates in the workpiece, continuously building up the weld pool depth while maintaining sputtering suppression through controlled thermal conduction mode operation throughout the entire process.
3Ease of manufacture
If bus bars are erected vertically for butt joint welding, then welding can be performed, but space efficiency is reduced
Solution Approach 1:
The patent inverts the conventional butt joint configuration by using lap joint configuration where bus bars are overlaid horizontally rather than erected vertically. This inversion of the joining geometry allows welding to be performed on horizontal surfaces, achieving both manufacturing feasibility and superior space efficiency by reducing the vertical space requirement.
Solution Approach 2:
The patent transitions from vertical arrangement (one dimension) to horizontal overlay arrangement (two-dimensional positioning). By changing the spatial dimension of the joint configuration from vertical erection to horizontal lap joint, the invention achieves efficient space utilization while maintaining welding feasibility through the multi-stage laser irradiation process.
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 method effectively suppresses sputtering and achieves deep penetration, allowing for reliable welding of thick bus bars with improved electrical conductivity and reduced heat generation.
Implementation Method 1
laser irradiation is performed a plurality of times under a condition of thermal conduction mode welding
Implementation Method 2
irradiating each of a first upper surface and a second upper surface with the laser along an edge of the first terminal
Implementation Method 3
Thermal conduction mode welding is a melting mode in which the sputtering does not occur
Data Source
AI summary
This laser welding method involves superposing a first terminal and a second terminal which are composed of a metal material containing copper and aluminum as a main component, and welding and joining the first terminal and the second terminal with a laser, the method including a laser irradiation step for irradiating, with a laser, along the edge of the first terminal, each of a first upper surface which is the opposite surface to a surface of the first terminal superposed on the second terminal, and a second upper surface which is the surface on the same side, of the second terminal superposed on the first terminal, wherein in the laser irradiation step, laser is emitted a plurality of times under the conditions for heat transfer mode welding.