Backlight Unit Side Opening Assembly for Mirror Vibration Resistance
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Solution Overview
Problem
Conventional backlight units for vehicle outside mirrors experience fine cracks and progressive breakage due to mechanical vibrations during ultrasonic welding, leading to detachment of electronic devices from the PCB and failure of the unit's function.
Innovation Solution
A backlight unit design featuring a case with a side opening for component assembly, a light source unit with a PCB and LEDs, a light guide plate for diffusing light, a reflection plate for light reflection, and a sealing material like epoxy to prevent cracks and enhance assembly workability, along with a manufacturing method involving double injection molding and epoxy sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ultrasonic welding is used to fix the top case and bottom case, then assembly efficiency is improved, but fine cracks occur in the soldering portion between PCB and electronic device due to mechanical vibration
Solution Approach 1:
The patent divides the housing into separate top case and bottom case components that are assembled together, allowing the ultrasonic welding to be applied only to the housing joints rather than the entire assembly including the PCB. This segmentation isolates the vibration impact from the soldering portions.
Solution Approach 2:
The PCB and electronic devices are mounted on the bottom case before the ultrasonic welding process. By preparing the PCB assembly in advance and securing it to the bottom case, the soldering joints are already established and protected when the top case is subsequently welded, preventing vibration-induced cracks.
2Device complexity
If conventional assembly methods are used without preliminary mounting, then manufacturing complexity is reduced, but progressive breakage occurs due to crack expansion during vehicle operation
Solution Approach 1:
The PCB and electronic devices are preliminarily mounted on the bottom case before assembling the top case. This preliminary action ensures that all soldering joints are established and protected from ultrasonic welding vibrations, preventing crack initiation and subsequent progressive breakage during vehicle operation.
Solution Approach 2:
The bottom case serves as a protective structure that cushions and isolates the PCB and electronic devices from the mechanical vibrations generated during ultrasonic welding of the top case. This beforehand cushioning prevents vibration transmission to the soldering joints.
3Ease of manufacture
If components are mounted through the front opening, then assembly simplicity is maintained, but the top case and bottom case require ultrasonic welding which causes cracks
Solution Approach 1:
The housing is segmented into top case and bottom case that are assembled separately. Components are mounted on the bottom case first, then the top case is attached via ultrasonic welding. This segmentation ensures that the welding process only affects the housing joint, not the PCB or electronic devices, eliminating vibration-induced cracks.
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
Prevents fine cracks and progressive breakage during ultrasonic welding, improves assembly workability, and reduces manufacturing costs by ensuring the backlight unit's functionality and durability.
Implementation Method 1
a light guide plate for diffusing, the light emitted from the light source unit across the entire area thereof
Implementation Method 2
a reflection plate stacked on the rear surface of the light guide plate and reflecting, the light emitted from the rear surface of the light guide plate toward the front surface of the light guide plate
Implementation Method 3
ultrasonic welding is a method of converting electric energy into mechanical energy by inputting an AC power of 50-60 Hz into a vibrator through an oscillator, and then causing instantaneous friction on the joint surface of the workpieces through a horn to fuse and bond them
Data Source
AI summary
The present invention relates to a backlight unit (10) for an outside mirror of an automobile, comprising: a case (20) provided with an inner space for accommodating a stacked assembly (95) of components, and having a side opening (22) through which the stacked assembly (95) can be inserted; and a light source unit (30) mounted into the inner space of the case (20) and capable of emitting light when power is supplied, wherein the stacked assembly (95) comprises: a light guide plate (40) for diffusing, across the entire area thereof, the light emitted from the light source unit; and a reflection plate (50) stacked on the rear surface of the light guide plate and reflecting, to the front surface of the light guide plate, the light emitted from the rear surface of the light guide plate.