Solar Battery Lead Wire Rectangular Cross Section Thin Plating
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Solution Overview
Problem
Solar batteries face warping issues due to thermal expansion mismatch between Si cells and conventional connecting lead wires, which reduces efficiency and limits the reduction in Si cell thickness.
Innovation Solution
A connecting lead wire with a rectangular cross-section and a thin plating layer, featuring a 0.2% proof stress of not more than 60 MPa and a volume resistivity of not more than 50 μΩ·mm, made from materials like Cu, Ag, or Au, with a plating layer containing elements like Ni, Ag, or Sn, to minimize thermal expansion mismatch and maintain high electric conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional connecting lead wire with thick plating layer is used, then connection reliability is improved, but 0.2% proof stress increases causing Si cell warping
Solution Approach 1:
The patent changes the plating layer thickness parameter from conventional thick plating (typically 10-20 μm) to thin plating (5 μm or less), which reduces the 0.2% proof stress of the connecting lead wire while maintaining adequate connection reliability. This parameter change allows the Si cell to remain flat after solder bonding without warping.
Solution Approach 2:
The patent applies different plating thicknesses to different regions of the connecting lead wire, with the plating layer being thin (5 μm or less) at the surface facing the Si cell to reduce stress, while maintaining appropriate plating thickness in other regions for adequate connection reliability and corrosion resistance.
2Quantity of substance
If Si cell plate thickness is reduced to lower material cost, then manufacturing cost is improved, but Si cell becomes warped or damaged due to temperature change
Solution Approach 1:
By changing the plating layer thickness parameter to 5 μm or less, the patent reduces the 0.2% proof stress of the connecting lead wire, which in turn reduces the warping force on thin Si cells during temperature changes. This enables the use of thinner Si cells with reduced material cost while maintaining structural stability.
3Stability of the object's composition
If invar cladding material is used to match thermal expansion, then thermal expansion matching is improved, but electric conductivity deteriorates
Solution Approach 1:
Instead of using invar cladding material throughout the entire connecting lead wire, the patent applies a thin plating layer (5 μm or less) only at the surface facing the Si cell. This localized approach maintains copper's high electric conductivity in the bulk material while providing adequate thermal expansion matching and connection reliability at the interface with the Si cell.
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 effectively reduces warping of Si cells while maintaining high electric conductivity, allowing for thinner Si cell designs without compromising connection reliability.
Implementation Method 1
a demand for a material with a low thermal expansion as a material of the connecting lead wire is elevated
Implementation Method 2
a pure Cu such as tough pitch Cu or oxygen-free Cu is used as a conductor
Data Source
AI summary
A metallic material is rolled to provide a conductor 3 having a rectangular cross section. A surface of the rectangular conductor 3 is plated with a plating layer 14. A thickness of the plating layer 14 at a surface facing to the Si cell is not more than 5 μm to provide a connecting lead wire 12 for a solar battery. The connecting lead wire 12 for a solar battery has 0.2% proof stress of not more than 60 MPa. The connecting lead wire 12 for a solar battery is connected to a predetermined contact region of a Si cell 1 of a solar battery at a high temperature.