Vehicle Pane Electrical Connection with Oval Solder Joints
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Solution Overview
Problem
Mechanical stresses in vehicle panes due to thermal expansion coefficient differences between electrical connection elements and the pane, leading to potential breakage, especially with the need to replace lead-containing solders with lead-free alternatives.
Innovation Solution
A disk with an electrical connection element featuring a substrate, an electrically conductive structure, and a solder mass with oval, elliptical, or circular contact surfaces, and a bridge design that minimizes mechanical stress through controlled solder distribution and capillary effect, using lead-free solders like tin-bismuth-silver alloys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-containing solder is used to connect the electrical connection element to the electrically conductive structure, then the ductility and ability to compensate mechanical stresses is improved, but the environmental compliance and adherence to ELV directive is worsened
Solution Approach 1:
The invention changes the chemical composition parameters of the solder material by defining specific alloying element ranges (Sn: 60-90 wt%, Pb: 0-40 wt%, with optional Ag, Cu, Bi, In additions) to create lead-free or low-lead solder formulations that maintain adequate ductility while meeting environmental requirements. This parameter optimization allows the solder to compensate thermal expansion stresses without violating ELV directives.
Solution Approach 2:
The invention uses composite solder materials consisting of multiple elements (primarily tin with controlled lead content and optional additions of silver, copper, bismuth, or indium) to achieve a balance between mechanical properties (ductility for stress compensation) and environmental compliance. The multi-element composition allows optimization of both reliability and environmental performance.
2Object-affected harmful factors
If lead-free solder is used to replace lead-containing solder, then the environmental compliance is improved, but the ductility and mechanical stress compensation capability is worsened
Solution Approach 1:
The invention optimizes the compositional parameters of lead-free solders by specifying precise ranges for tin (60-90 wt%) and controlled lead content (0-40 wt%), along with optional additions of silver (0-10 wt%), copper (0-10 wt%), bismuth (0-10 wt%), or indium (0-5 wt%). This parameter control ensures that even with reduced or eliminated lead, the solder maintains sufficient ductility to compensate for thermal expansion differences between the electrical connection element and the glass substrate.
3Stress or pressure
If the contact surface between the electrical connection element and the electrically conductive structure has a large area, then the mechanical stress distribution is improved, but the soldering process complexity and heat distribution uniformity is worsened
Solution Approach 1:
The invention applies local quality by defining specific geometric characteristics for the contact surface (at least one segment of oval, ellipse, or circle with central angle ≥90°) that create optimal local stress distribution patterns. This geometric optimization ensures uniform stress distribution across the contact area while maintaining a relatively simple soldering process, as the curved geometry naturally promotes even heat and stress distribution without requiring complex multi-step procedures.
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 solution reduces mechanical stresses and ensures uniform solder melting, enhancing adhesion and stability of the connection element on the pane, even with lead-free solders that have lower ductility.
Implementation Method 1
ensuring uniform heat distribution and adhesion
Implementation Method 2
a bridge design that minimizes excess solder
Data Source
Figure 1~1a
Figure 2a~2b
Figure 2c~3
AI summary
The present invention relates to a disk comprising: - a substrate (1), - an electrically conductive structure (2) on a region of the substrate (1), - a layer of solder (4) on a region of the electrically conductive structure (2), - at least one electrical connection element (3) comprising a chromium-containing steel with a chromium content of greater than or equal to 10.5 wt.%, - at least two solder joints (15, 15') of the connection element (3) on the solder (4), wherein - the solder joints (15, 15') form at least one contact surface (8) between the connection element (3) and the electrically conductive structure (2) and - the shape of the contact surface (8) has at least one segment of an oval, an ellipse or a circle with a central angle α of at least 90°.