Vehicle Window Glass Ceramic Layer for Lead-Free Solder Cracking
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Solution Overview
Problem
Vehicle window glasses using lead-free solder are prone to cracking due to the high elastic modulus and rigidity of the solder, which causes stress from thermal expansion differences with the glass plate, leading to potential peeling and cracking issues.
Innovation Solution
A vehicle window glass configuration that includes a glass plate with a curved shape, a color ceramic layer, an electrically conductive layer formed with silver, and a lead-free solder, where the color ceramic layer and electrically conductive layer thicknesses are optimized to reduce stress and prevent cracking, with the color ceramic layer acting as a stress reliever and the electrically conductive layer being formed efficiently with a single screen printing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free solder is used to replace leaded solder, then environmental harm is reduced, but the solder becomes more rigid and prone to causing cracks in the glass plate
Solution Approach 1:
A resin layer is introduced as an intermediary between the rigid lead-free solder and the glass plate. This resin layer has lower rigidity than the solder, acting as a stress-absorbing buffer that prevents stress concentration at the solder-glass interface, thereby preventing cracks while maintaining the environmental benefits of lead-free solder
Solution Approach 2:
The rigidity parameter of the bonding system is modified by introducing a resin layer with specifically controlled rigidity (lower than the solder). This parameter change creates a gradient structure that gradually transitions from the rigid solder to the glass plate, reducing stress concentration and preventing cracks
2Reliability
If the conductor layer is made thinner with narrower width, then crack propagation is reduced, but the electrical conductivity and mechanical strength are compromised
Solution Approach 1:
The resin layer serves as a stress-absorbing intermediary that protects the conductor layer from stress concentration. This allows the conductor layer to maintain adequate thickness and width for proper electrical conductivity and mechanical strength, while the resin prevents cracks from propagating through the conductor layer
3Strength
If lead-free solder with high rigidity is used, then bonding strength is improved, but stress from thermal expansion differences causes peeling and cracking
Solution Approach 1:
The resin layer acts as a stress-absorbing intermediary between the high-rigidity solder and the glass plate. It maintains the bonding strength provided by the rigid solder while absorbing thermal expansion stress through its lower rigidity, preventing peeling and cracking at the interface
Solution Approach 2:
The rigidity parameter is differentiated across layers: the solder maintains high rigidity for bonding strength, while the resin layer has lower rigidity to absorb thermal stress. This parameter differentiation allows both bonding strength and stress resistance to be achieved simultaneously
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 optimized configuration effectively reduces the likelihood of cracking in the glass plate even under repeated heating and cooling cycles, maintaining the bonding strength and preventing detachment at the joining points, thus enhancing the durability of the vehicle window glass.
Implementation Method 1
the color ceramic layer acting as a stress reliever
Implementation Method 2
a lead-free solder, wherein the electrically conductive layer is connected to a terminal through which electricity is conducted to the electrically conductive layer, by means of the lead-free solder
Data Source
Figure 1
Figure 2
AI summary
To provide a vehicle window glass which is not susceptible to cracks, and a method for manufacturing the vehicle window glass. A vehicle window glass 1 of the present invention is provided with: a glass plate 11, a color ceramic layer 12, formed on the surface of the glass plate 11 and having a thickness more than 10 µm but equal to or less than 25 µm, and an electrically conductive layer 13 formed on the surface of the color ceramic layer 12 and having silver as a main component. The electrically conductive layer 13 and a terminal electrically connected to the electrically conductive layer 13 are connected to each other using a lead-free solder 14. In the vehicle window glass 1 of the present invention, since the thickness of the color ceramic layer 12 is more than 10 µm, the glass plate 1 is not susceptible to cracks.