Laser Beam Shaping for DBC Lap Welding
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Solution Overview
Problem
Existing methods for welding Direct Bonded Copper (DBC) structures, such as ultrasonic welding, often result in cracks and heat buildup in the ceramic substrate due to the thin copper layer, leading to unreliable and non-reproducible results.
Innovation Solution
A laser machining machine with an optical beam-shaping system that images a laser beam into a machining plane with a bell-shaped power density distribution along the depth, ensuring a consistent and reproducible welding process by maintaining power uniformity over several millimeters, preventing heat buildup and damage to the ceramic substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrasonic welding is used to weld copper tracks to terminal contacts on DBC structures, then welding can be performed, but cracks and heat buildup occur in the ceramic substrate leading to unreliable results
Solution Approach 1:
The patent replaces ultrasonic welding (mechanical/vibrational method) with laser welding (optical/thermal method). The laser beam delivers energy precisely to the copper contact area without the mechanical contact and vibration that cause cracks and heat buildup in the ceramic substrate during ultrasonic welding.
Solution Approach 2:
The patent uses a lens system to focus the laser beam to a small spot size, concentrating energy locally on the copper track-terminal contact interface. This localized heating welds the copper components without excessive heat diffusion to the ceramic substrate, preventing thermal damage while achieving reliable welds.
2Productivity
If laser welding is used with conventional beam shaping, then welding speed can be increased, but the thin copper layer on ceramic substrate is damaged due to excessive heat concentration
Solution Approach 1:
The patent employs a galvanometer-driven mirror system that dynamically controls the laser beam position and movement across the workpiece. This dynamic control allows precise tracking of the weld path, adjusting beam position in real-time to maintain optimal focus on the copper layer while preventing heat accumulation in the ceramic substrate.
Solution Approach 2:
The patent uses a variable aperture iris diaphragm to dynamically adjust the beam diameter and power density during welding. By changing these parameters in real-time, the system maintains sufficient energy concentration for welding speed while preventing excessive heat buildup that would damage the ceramic substrate.
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 enables reliable and reproducible in-depth welding of DBC structures without damaging the ceramic substrate, ensuring precise and consistent connections between copper components while preventing heat accumulation.
Implementation Method 1
an optical imaging system (9) for imaging a laser beam (5) into a machining plane (10) with an imaging depth of at least ±2 mm, in such a way that the radial power density distribution of the laser beam (5) is bell-shaped
Implementation Method 2
methods for laser welding of workpieces, such as for lap welding of direct bonded copper (DBC) structures, in a machining plane by a laser beam (5)
Data Source
AI summary
In a laser machining machine (1) for laser welding of workpieces, in particular for lap welding of DBC structures, comprising a laser beam generator for generating a laser beam and an optical imaging system for imaging the laser beam into a machining plane, according to the invention, the optical imaging system comprises an optical beam-shaping system, which images the laser beam in the machining plane with an imaging depth (Δd) of at least ±2 mm, preferably of at least ±5 mm, in such a way that the radial power density distribution (Pr) of the laser beam is bell-shaped along the imaging depth (Δd) in each plane at right angles to the beam axis and the maximum values (Pmax) of these bell-shaped power density distributions (Pr) along the imaging depth (Δd) vary in relation to one another by less than 10%, preferably by less than 5%.