Solar Cell Solder Joint Thickness Control via Cantilevered Tabs
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Solution Overview
Problem
Existing methods for electrically connecting solar cells often result in thin solder joints that are prone to failure due to thermal fatigue and mechanical strains, leading to increased failure rates and defects in solar cell arrays.
Innovation Solution
A method involving the formation of a thicker solder layer around a thin solder layer by using interconnects with cantilevered tabs and a controlled solder paste application process, where the solder paste is heated and spread to form a uniform, thickened solder joint that inhibits crack growth and enhances mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard soldering technique is used to electrically connect interconnects with solar cells, then the manufacturing process is simple and fast, but the solder layer becomes wedge-shaped with thin areas that are prone to failure due to thermal fatigue and mechanical strains
Solution Approach 1:
The patent applies preliminary action by pre-forming depressions in the interconnect tabs before the soldering process. These depressions are created in advance to control the solder flow and distribution, ensuring that the solder fills the depression completely to form a thick, uniform layer rather than a wedge-shaped layer. This preliminary structural modification to the interconnect enables reliable solder joint formation without requiring complex real-time process control during soldering.
2Strength
If a thicker solder layer is formed around a thin solder layer, then crack growth is reduced and mechanical stability is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies local quality by creating a localized thick solder layer specifically within the depression region of the interconnect tab, while the rest of the tab maintains its original thickness. This localized thickening provides enhanced mechanical strength and crack resistance exactly where the solder joint is needed, without unnecessarily increasing the complexity of the entire interconnect structure or requiring uniform thickening across the whole component.
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 significantly reduces the failure rate of solder joints by creating a thicker, more stable solder layer that prevents crack propagation and improves the mechanical and thermal fatigue resistance of the connections, thereby enhancing the reliability of solar cell arrays.
Implementation Method 1
forming a solder paste into a liquid state uniformly spread around the depression between the interconnect tabs and solder pads
Implementation Method 2
forming a solder paste into a liquid state uniformly spread around the depression between the interconnect tabs and solder pads thereby forming an electrical connection between the first and second solar cells
Data Source
AI summary
A method for connecting a plurality of solar cells and an improved interconnect is disclosed. The method includes aligning an interconnect to a plurality of solar cells having solder pads, where the interconnect has a main body and tabs extending therefrom, and where each of the tabs has a downward depression, such that the tabs are positioned above the solder pads in between solar cells and pinning the interconnect against a work surface by pressing a hold down pin against the main body of the interconnect such that a lower surface of the interconnect tabs are maintained parallel to an upper surfaces of the solder pads, and such that the depression of each of the tabs flatly contacts the solder pads. The method can also include cantilevered tabs extending downwardly from the main body providing a controlled spring force between the tab lower surface and the solder pad upper surface.