Vehicle Windowpane Soldering with Tin-Silver Alloy and Preheating
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Solution Overview
Problem
Conventional lead-free solder alloys, such as tin-silver based alloys, suffer from reduced joining strength and increased cracking risk during thermal shock tests due to high elastic modulus, and also impair the appearance of vehicle windowpane conductor layers.
Innovation Solution
A method involving a silver paste with 65-85% silver powder and a specific resistance of 2.5-6.5 µΩcm, combined with a lead-free solder alloy composed mainly of tin (95% or more) and preheating the glass sheet to a temperature just above ambient but below the solder's melting point, to prevent cracking and maintain appearance quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tin-based lead-free solder alloy is used for soldering the connection terminal onto the terminal connection part, then environmental compliance is improved, but joining strength deteriorates and cracking risk increases
Solution Approach 1:
The invention changes the chemical composition parameters of the solder alloy by adding silver (0.1-10 wt%) and controlling tin content (85-99.9 wt%), which modifies the elastic modulus and thermal expansion characteristics to achieve both environmental compliance and adequate joining strength
Solution Approach 2:
The invention creates a composite solder alloy system combining tin, silver, and optional copper/manganese elements, where each component contributes specific properties: tin provides base solderability, silver enhances strength and reduces elastic modulus, and the combination achieves both environmental compliance and mechanical performance
2Strength
If a tin-silver based lead-free solder alloy is used, then joining strength is improved, but cracking is easily caused on the glass sheet during thermal shock test
Solution Approach 1:
The invention precisely controls the silver content (0.1-10 wt%) to optimize the balance between joining strength and elastic modulus, preventing excessive stiffness that would cause cracking while maintaining adequate bond strength
Solution Approach 2:
The invention applies preheating treatment specifically to the glass sheet before soldering, creating a localized temperature control measure that reduces thermal stress concentration at the solder joint area during subsequent thermal shock
3Reliability
If a tin-based lead-free solder alloy is used, then environmental compliance is improved, but appearance quality deteriorates
Solution Approach 1:
The invention adjusts the solder alloy composition by adding silver and controlling the tin-to-silver ratio, which modifies the metallurgical interaction with the silver paste conductor layer to prevent excessive diffusion and maintain appearance quality
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 method ensures robust joining strength and prevents cracking in vehicle windowpanes even under thermal shock, while maintaining high appearance completeness by controlling thermal stress and silver distribution.
Implementation Method 1
a conductor layer which is formed on a surface of a glass sheet by sintering a silver paste containing a silver powder and a glass frit
Implementation Method 2
preheating the glass sheet to a temperature just above ambient but below the solder's melting point, to prevent cracking and maintain appearance quality
Data Source
Figure 1
Figure 2
AI summary
The present invention is concerned with, as an embodiment, a windowpane for vehicles including a glass sheet, a conductor layer which is formed on the surface of the glass sheet by sintering a silver paste containing a silver powder and a glass frit and which has at least a strip part and a terminal connection part connected to the strip part, and a connection terminal soldered onto the terminal connection part with a lead-free solder alloy, in which the conductor layer has a specific resistance of from 2.5 to 6.5 µΩcm, the strip part has a line width of not more than 0.35 mm, the lead-free solder alloy consists essentially of tin and silver and has a content of tin of 95 % by mass or more, and cracking is not caused on the glass sheet even after elapsing 500 cycles in a prescribed thermal shock test; and a method for producing same. The windowpane for vehicles is one in which in soldering a tin-silver based lead-free alloy onto the glass sheet, even when exposed to high temperature or low temperature, a good joining strength is kept, cracking of the glass sheet is prevented from occurring, and the completeness of an appearance design is high.