Silver Epoxy Bus Bar Connection for Heatable Vehicle Windows
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Solution Overview
Problem
Solder joints in heatable vehicle windows cause stress between glass substrates, leading to potential cracking and increased manufacturing costs, as well as higher impedance and hot spots, due to their thick profile and the need for specialized equipment and fluxing agents.
Innovation Solution
Using a silver inclusive epoxy to electrically connect bus bars and external connectors, which provides a thin, uniform, and low-impedance connection, reducing stress and eliminating the need for soldering and its associated issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder joints are used to connect bus bars and external connectors, then electrical connection is achieved, but the thick profile causes stress between glass substrates and potential cracking
Solution Approach 1:
The patent changes the physical parameters of the connection material from traditional solder (metallic, thick profile) to epoxy resin with silver particles (polymer-based, thin profile). This parameter change reduces the connection thickness from typically >0.5mm to <0.1mm, eliminating stress concentration on glass substrates while maintaining electrical conductivity through the silver particles dispersed in the epoxy matrix.
Solution Approach 2:
The patent employs a composite material system consisting of epoxy resin as the base matrix and silver particles as conductive fillers. This composite approach combines the mechanical properties of epoxy (flexibility, adhesion, stress distribution) with the electrical properties of silver (high conductivity), achieving both reliable electrical connection and reduced mechanical stress on the glass substrates.
2Reliability
If solder joints are used, then electrical connection is made, but impedance increases and hot spots are generated
Solution Approach 1:
The patent optimizes the electrical conductivity parameters by controlling the silver particle concentration, size distribution, and morphology in the epoxy matrix. By adjusting these parameters, the connection achieves low electrical impedance comparable to or better than traditional solder, preventing hot spot formation while maintaining the mechanical advantages of the epoxy-based system.
Solution Approach 2:
The patent replicates the essential function of solder joints (electrical connection and mechanical bonding) using a different material system (epoxy with silver particles). The silver particles copy the high conductivity function of solder, while the epoxy matrix copies the bonding function, creating a composite solution that achieves the desired electrical performance without the harmful thermal and mechanical effects of traditional soldering.
3Reliability
If soldering process is used, then electrical connection is achieved, but manufacturing complexity and costs increase due to specialized equipment and fluxing agents
Solution Approach 1:
The patent replaces the complex soldering process (requiring specialized soldering equipment, temperature control systems, and flux application mechanisms) with a simpler epoxy dispensing and curing process. The epoxy can be applied using standard dispensing equipment, and the curing process occurs at lower temperatures than soldering, eliminating the need for fluxing agents and complex thermal management systems.
Solution Approach 2:
The patent uses epoxy resin, a relatively inexpensive and easily handled material, as the connection medium. The epoxy can be dispensed in controlled amounts and cured in place, eliminating the need for expensive soldering equipment, flux containers, and associated disposal systems. The simplicity of the epoxy-based approach reduces both capital equipment costs and ongoing manufacturing expenses.
4Reliability
If solder joints are used, then electrical connection is made, but the thick profile requires cutting notches in glass substrates, increasing manufacturing time and costs
Solution Approach 1:
The patent fundamentally changes the thickness parameter of the connection material from >0.5mm (solder) to <0.1mm (epoxy with silver particles). This dramatic reduction in thickness eliminates the need for notching or special accommodations in the glass substrate design, allowing for direct bonding to the glass surface and significantly simplifying the manufacturing process while maintaining reliable electrical connection.
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 silver inclusive epoxy improves electrical connectivity, reduces hot spots and stress on the window, lowers impedance, and allows for re-positioning of connectors, thereby minimizing the risk of glass breakage and simplifying the manufacturing process.
Implementation Method 1
silver inclusive epoxy electrically connecting at least one of the conductive bus bars to at least one external connector
Implementation Method 2
silver inclusive epoxy to electrically connect bus bars and external connectors
Implementation Method 3
The electro conductive layer(s) generates heat when electric current is passed therethrough via the bus bars. In such a manner, snow and ice may be melted from vehicle windows
Data Source
AI summary
A heatable vehicle window (e.g., windshield or backlite) has bus bars electrically connected to a heatable coating having one or more heatable conductive layers. Electrical connection(s) between at least one bus bar and a corresponding external connector in the heatable window is/are made using a silver inclusive epoxy. The use of the silver inclusive epoxy permits a thin substantially uniform electrical connection to be made and permits numerous example advantages to be realized.