Vehicle Window Glass Terminal Layout for Lead-Free Solder Stress
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Solution Overview
Problem
Vehicle window glasses with metal terminals connected using lead-free solder experience cracks in the optically shielding layer or conductor, leading to partial peeling off of the glass plate surface due to residual stress, which can occur days after soldering.
Innovation Solution
A vehicle window glass design with a metal terminal that includes a glass plate, an optically shielding layer, a conductor connected to the terminal via a lead-free solder, and a conductive wire, where the terminal connection portion and coupling portion are connected throughout at most 30% of the terminal's periphery, with the terminal connection portion's edge located less than 3 mm away from the pedestal edge, reducing stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free solder is used to connect the metal terminal to the conductor, then environmental safety and human health are improved, but residual stress in the glass plate increases causing cracks and surface peeling
Solution Approach 1:
The patent changes the chemical composition parameters of the solder alloy from lead-based to lead-free formulations, specifically using锡-银-铜 (Sn-Ag-Cu) or 锡-铜 (Sn-Cu) alloys. This parameter change eliminates lead contamination while managing the resulting increase in residual stress through controlled stress distribution design
Solution Approach 2:
The patent applies local quality by creating a specific structural configuration at the connection interface between the metal terminal and conductor. The conductor is designed with a pad structure that has a larger area than the terminal's contact area, creating a stress distribution gradient that locally manages the residual stress concentration at the solder joint
2Reliability
If the conductor is directly connected to the metal terminal with lead-free solder, then electrical connection is achieved, but stress concentration causes cracks in the optically shielding layer or conductor
Solution Approach 1:
The patent segments the connection structure into distinct functional zones: the metal terminal, the solder joint, and the conductor pad. The conductor is designed with a pad portion that is separated from the main conductor trace, creating a stress isolation zone that prevents crack propagation from the high-stress solder joint to the optically shielding layer
Solution Approach 2:
The patent implements beforehand cushioning by designing the conductor pad with larger dimensions than the terminal contact area. This creates a stress buffer zone that absorbs and distributes the residual stress from the lead-free solder before it can reach the optically shielding layer or conductor trace, preventing premature cracking
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
This design reduces the occurrence of cracks in the optically shielding layer and conductor, preventing partial peeling off of the glass plate surface, while maintaining a required bonding strength between the metal terminal and conductor.
Implementation Method 1
The conductor includes the terminal connection portion connected to the pedestal portion by means of the lead-free solder
Data Source
AI summary
A vehicle window glass with a metal terminal, includes a glass plate, an optically shielding layer on at least one of principal surfaces of the glass plate, a conductor on the optically shielding layer, a metal terminal electrically connected to the conductor via a lead-free solder, and a conductive wire fixed to the metal terminal; the metal terminal includes a pedestal portion electrically connected to a terminal connection portion via the lead-free solder; the conductor includes the terminal connection portion connected to the pedestal portion by means of a lead-free solder, and a coupling portion connected to the terminal connection portion with a narrow width than a width of the terminal connection portion in a longitudinal direction or a transverse direction of the terminal connection portion; the terminal connection portion and the coupling portion are connected together throughout at most 30% of an entire periphery of the terminal connection portion.