Middle Frame Laser Welding with Roughened Post-Hole Interfaces
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Solution Overview
Problem
The low laser absorptivity of the smooth surfaces in the metal middle frame of mobile terminals leads to poor welding quality, including insufficient molten pool depth, bubbles, cracks, and burst points, which affects the overall device performance.
Innovation Solution
The introduction of rough surfaces on the welded posts and through-holes of the middle frame, achieved through film processing and chemical sanding, increases the laser absorption amount, thereby improving the welding quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the welding surface is machined to be smooth, then the surface quality is improved, but the laser absorptivity decreases below 30%
Solution Approach 1:
The patent applies different surface qualities to different regions: the visible surface remains smooth for aesthetic purposes, while the welding surface is treated to be rough for high laser absorptivity. This local differentiation resolves the contradiction between surface quality and laser absorption.
Solution Approach 2:
The patent changes the surface roughness parameter of the welding area to increase laser absorptivity from below 30% to above 60%. By controlling the roughness parameter (Ra 3.2-5μm), the laser energy absorption is significantly improved while maintaining overall surface quality.
2Use of energy by moving object
If the laser absorptivity is low, then the surface reflectivity is high, but the welding quality deteriorates with insufficient molten pool depth
Solution Approach 1:
The patent creates a local rough surface treatment specifically at the welding position while keeping other surfaces smooth. This localized approach ensures high laser absorptivity (above 60%) at the welding area, producing adequate molten pool depth and reliable welding quality without affecting overall surface appearance.
Solution Approach 2:
By changing the surface roughness parameter to Ra 3.2-5μm at the welding surface, the patent transforms the laser interaction from high reflection to high absorption, ensuring sufficient energy coupling and molten pool formation for reliable welding.
3Loss of energy
If the laser absorptivity is low, then less laser energy is absorbed, but welding defects such as bubbles, cracks, and burst points increase
Solution Approach 1:
The patent changes the surface roughness parameter to Ra 3.2-5μm, which increases laser energy absorption from below 30% to above 60%. This energy absorption improvement prevents welding defects by ensuring sufficient thermal energy is coupled into the material for complete melting and proper weld formation.
Solution Approach 2:
The rough surface treatment is applied locally only to the welding area, concentrating the energy absorption enhancement where needed. This ensures adequate laser energy absorption at the weld zone to prevent defects like bubbles and cracks, while maintaining smooth surfaces elsewhere.
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 increased laser absorptivity results in improved welding quality, including a deeper molten pool and reduced defects, which enhances the overall performance of the electronic device.
Implementation Method 1
the rough surface is configured to increase a laser absorption amount in the fit part of the welded post and the through-hole during the laser welding
Implementation Method 2
Laser radiation heats a surface of a work piece. Surface heat diffuses to inside by using heat conduction, and a parameter such as a width, energy, a peak power and a repetition frequency of a laser pulse is controlled, so that the work piece melts to form a specific molten pool
Implementation Method 3
Surface heat diffuses to inside by using heat conduction, and a parameter such as a width, energy, a peak power and a repetition frequency of a laser pulse is controlled, so that the work piece melts to form a specific molten pool
Data Source
Figure 1~2a
Figure 2b
Figure 3
AI summary
Embodiments of this application provide an electronic device and a manufacturing method for a middle frame, so as to resolve a problem that low laser absorptivity affects welding quality during laser welding, and further affects quality of an entire device. The middle frame provided in the embodiments of this application includes a bezel and a middle plate. The bezel is disposed around an edge of the middle plate. A plurality of welded posts are disposed on the middle plate. A plurality of through-holes whose positions and sizes are corresponding to those of the plurality of the welded posts are disposed on the bezel, and the plurality of welded posts form a hole shaft fit in a one-to-one correspondence with the plurality of through-holes. Surfaces of the plurality of welded posts and surfaces of the plurality of through-holes are rough surfaces. The bezel and the middle plate are connected by using laser welding in each fit part of the welded post and the through-hole. The rough surface is configured to increase a laser absorption amount in the fit part of the welded post and the through-hole during the laser welding. In this application, the rough surface is disposed to effectively improve welding laser absorptivity. A rounded rectangular welded post is disposed to improve strength of the welded post, and an exhaust groove is added to a root of the welded post, thereby improving welding quality.