Electrochromic Rearview Mirror Assembly With Stress-Relieved Solder Joints
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Automotive auto-dimming electrochromic mirror reflective element assemblies face issues with cracking and spalling of glass substrates due to stresses and strains during manufacturing and use, particularly at the solder joints where electrical connectors are attached, leading to potential part failure.
Innovation Solution
The solution involves locally removing the metallic reflector coating at the solder joint area on the rear glass substrate to decouple the solder joint from the metallic reflector, reducing direct contact and stress on the glass substrate, thereby mitigating cracking and spalling by creating a solder and glass surface joint instead of a solder-metallic reflector bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder is directly applied to the metallic reflector coating on the glass substrate, then electrical connection is established, but stresses and strains are concentrated on the glass substrate causing cracking and spalling
Solution Approach 1:
A non-conductive adhesive layer is introduced as an intermediary between the metallic reflector coating and the solder joint. This adhesive layer serves as a stress buffer that prevents direct transmission of mechanical stresses from the solder joint to the glass substrate, while still allowing electrical connection through the adhesive to the metallic coating.
Solution Approach 2:
The adhesive layer is applied locally only at the solder joint area where stress concentration occurs, rather than uniformly across the entire glass substrate. This localized application provides stress relief precisely where needed without compromising the overall structural integrity or optical properties of the mirror assembly.
2Illumination intensity
If metallic reflector coating is applied across the entire rear glass substrate surface, then optical reflection performance is maximized, but stress concentration at solder joints increases leading to cracking and spalling
Solution Approach 1:
The metallic reflector coating is selectively applied to cover most of the rear glass substrate surface for optimal optical reflection, but is intentionally omitted or reduced at the solder joint areas. This local modification reduces stress concentration zones while maintaining overall reflection performance in the functional mirror areas.
Solution Approach 2:
The non-conductive adhesive layer acts as a mediator between the metallic reflector coating and the solder joint, allowing the coating to be present near solder joints without creating direct stress pathways to the glass substrate.
3Ease of manufacture
If solder joints are established on the metallic reflector coating, then electrical connectivity is achieved, but manufacturing defects such as cracking and spalling increase
Solution Approach 1:
The non-conductive adhesive layer serves as an intermediary that enables solder joint formation without directly bonding to the glass substrate. This maintains manufacturing simplicity while preventing the harmful stress transmission that causes cracking and spalling during the soldering process.
Solution Approach 2:
The metallic reflector coating is locally removed or excluded from the solder joint area, extracting the problematic direct bond between solder and glass substrate. This allows standard soldering procedures to continue while eliminating the source of manufacturing defects.
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 approach significantly reduces the occurrence of cracks and spalling at the glass substrate, enhancing the durability and reliability of the electro-optic mirror reflective element assemblies by minimizing stress and strain on the glass, thus preventing part failure.
Implementation Method 1
Automotive auto-dimming electrochromic mirror reflective element assemblies are known and typically include a front substrate and a rear substrate and an electrochromic medium sandwiched therebetween
Data Source
AI summary
A multi-camera vehicular video display system includes an interior rearview mirror assembly having a mirror head that includes a transflective mirror element and a video display screen disposed behind the transflective mirror element. The mirror assembly includes a mechanism that is operable to change orientation of the transflective mirror element relative to a driver of the vehicle. When the mechanism changes orientation to a second position that is tilted away from the eyes of the driver of the vehicle, the video display screen displays video images viewable through the transflective mirror element. When the mechanism changes orientation to a first position that is tilted towards the eyes of the driver of the vehicle, the video display screen does not display video images. The displayed video images are derived, at least in part, from image data captured by at least one exterior viewing camera of the vehicle.