Vehicle Windshield Terminal Joint With Inorganic Thin Film Buffer
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Solution Overview
Problem
The use of lead-free solder in glass windshields for vehicles leads to residual stress and cracking due to thermal expansion differences between the glass and solder, reducing the breaking strength of the glass plate with attached terminals.
Innovation Solution
Incorporating an inorganic thin film with a metal compound layer between the glass plate and the terminal joint portion, made of materials like Zr-doped TiO2 and SiO2, to enhance the breaking strength by improving the bonding strength of lead-free solder and reducing residual stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-free solder is used to join terminals to the conductor on the glass plate, then environmental compliance is improved, but residual stress and cracking occur due to thermal expansion differences
Solution Approach 1:
An inorganic thin film is introduced as an intermediary layer between the glass plate and the lead-free solder. This intermediate layer has thermal expansion properties that bridge the gap between glass and solder, reducing residual stress and preventing cracking while maintaining environmental compliance with lead-free soldering
Solution Approach 2:
The thermal expansion coefficient parameter is modified by introducing the inorganic thin film layer. This layer changes the thermal expansion characteristics of the joint system, allowing for better compatibility between components with different thermal expansion properties (glass and lead-free solder)
2Reliability
If lead-free solder is used instead of leaded solder, then environmental restrictions are satisfied, but the elastic modulus increases and stress relaxation decreases
Solution Approach 1:
The inorganic thin film serves as a stress-buffering intermediary between the rigid glass plate and the high-modulus lead-free solder. This intermediate layer absorbs and distributes residual stresses, preventing them from concentrating in the glass plate and causing harmful cracks
3Ease of manufacture
If the terminal joint portion is formed directly on the glass plate, then manufacturing is simplified, but bonding strength is insufficient and cracks occur
Solution Approach 1:
The inorganic thin film acts as a bonding intermediary that enhances adhesion between the glass plate and lead-free solder. This intermediate layer provides a surface that is more compatible with both materials, improving bonding strength without significantly complicating the manufacturing process
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 inorganic thin film enhances the breaking strength of the glass plate with attached terminals by improving the bonding of lead-free solder and reducing thermal stress, preventing cracks and improving the structural integrity of the windshield.
Implementation Method 1
due to the difference between the thermal expansion coefficient of the glass plate and that of the lead-free solder, a difference occurs between the amount of the thermal shrinkage of the glass plate and that of the lead-free solder, thus causing a stress
Implementation Method 2
forming an inorganic thin film in at least a formation area of the terminal joint portion on the interior surface of the first glass plate by a vapor deposition method
Data Source
AI summary
A windshield for vehicle includes a glass plate with a terminal including a first glass plate, a conductor made of a material containing silver and glass frit and including a terminal joint portion, and a terminal joined to the terminal joint portion of the conductor through lead-free solder, in which the glass plate with the terminal further includes an inorganic thin film between the first glass plate and the terminal joint portion, the inorganic thin film including at least one metal compound layer, having an overall thickness of 1,000 nm or smaller, and having a single-layer structure or a laminated structure, and at least an outermost surface of the inorganic thin film having an insulating property.