Laser-Structured Substrate Joining for Strong Metal-Polymer Adhesion
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Solution Overview
Problem
Existing methods for assembling substrates and parts often result in interfacial ruptures rather than cohesive ruptures, leading to suboptimal mechanical properties and requiring multiple light sources during the welding process.
Innovation Solution
A method involving pulsed laser structuring of the substrate surface with a single light source to create a patterned surface, followed by contact with a part having a lower melting point material, and subsequent heating to achieve strong adhesion and high tensile and shear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If two light sources (monochromatic and polychromatic) are used for irradiation heating, then adhesion between substrate and polymer material is improved, but device complexity increases
Solution Approach 1:
The patent combines the functions of two separate light sources (monochromatic and polychromatic) into a single polychromatic light source that provides both wavelength components simultaneously. This merging approach maintains the adhesion enhancement benefits while eliminating the complexity of operating and aligning two separate laser systems.
Solution Approach 2:
The patent employs a polychromatic light source that performs multiple functions: it provides both monochromatic and polychromatic wavelength components for irradiation heating, structures the substrate surface, and heats the polymer material. This single multi-functional source replaces what previously required two specialized sources.
2Strength
If surface structuring is applied to increase adhesion, then mechanical properties are improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies surface structuring as a preliminary step before bonding, using laser irradiation to create microstructures on the substrate surface in advance. This pre-structuring prepares the surface for enhanced adhesion without requiring complex post-processing or additional manufacturing steps during assembly.
Solution Approach 2:
The patent replaces mechanical surface structuring methods (such as mechanical etching or chemical treatment) with optical field-based laser structuring. This substitution eliminates the need for mechanical contact, tooling, and complex fixture systems, simplifying the manufacturing process while achieving the same adhesion enhancement.
3Strength
If heating is applied to melt fusible material for bonding, then adhesion is improved, but risk of substrate damage increases
Solution Approach 1:
The patent applies heating locally to only the fusible material layer and the immediate interface region, rather than heating the entire substrate uniformly. This localized heating approach melts the fusible material for bonding while keeping the substrate temperature below its melting or damage threshold, preventing harmful thermal effects.
Solution Approach 2:
The patent carefully controls heating parameters (temperature, time, spatial distribution) to achieve selective melting of the fusible material. By adjusting these parameters, the process melts the low-melting-point material for strong bonding while maintaining the substrate temperature within safe limits, avoiding thermal damage.
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 method produces assemblies with cohesive ruptures, enhanced mechanical properties, and eliminates the need for multiple light sources, achieving strong adhesion and resistance without damage during mechanical force transfer.
Implementation Method 1
provide a pulsed structuring laser capable of generating a pulsed structuring laser beam suitable for etching the upper surface of the substrate
Implementation Method 2
provide a heating device capable of creating a temperature increase in the fusible material sufficient to melt it
Implementation Method 3
heat, by means of the heating device, the fusible material so as to reach in the fusible material, a temperature sufficient to melt at least a part of it
Data Source
Figure 1~2
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AI summary
The present invention relates to a method for joining a substrate (11) with a part (14) comprising a step of structuring the substrate with a pulsed laser (31), the substrate (11) preferably being made of metal and the part preferably being polymer-based. The structuring step allows grooves to be etched into the substrate (11) in a pattern (17) determined by the relative movement (41) of the beam (32) and the substrate (11). The pattern (17) is designed so as to allow an excellent adhesion to be achieved between the structured substrate (12) and a part (14) after the substrate (12) and the part (14) have been joined by laser welding (130). Preferably, the joining method comprises a step (50) of pre-treating the structured surface in order to allow better absorption of the laser during the joining by welding.