Solar Battery Low-Temperature Sn-Bi Solder Connection
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Solution Overview
Problem
Existing solar battery technologies face challenges in achieving reliable and cost-effective electrical connections between solar cell electrodes and wiring substrates due to high-temperature soldering requirements, thermal expansion issues, and high electrical resistance using Anisotropic Conductive Films (ACF).
Innovation Solution
A solar battery design that uses a conductive adhesive agent, such as an Sn—Bi-based solder, with a low melting point and low electric resistivity, applied between the solar cell and wiring substrate, along with an insulative base material like polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), to facilitate low-temperature connections and mechanical compression bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If general lead-free solder (Sn-Ag-Cu-based solder) is used to connect solar cell electrodes and wiring substrate wires, then reliable electrical connection is achieved, but high heating temperature (around 250°C) is required which generates thermal stress and causes cracking or connection failure
Solution Approach 1:
The patent changes the material parameter of the solder from conventional Sn-Ag-Cu alloy to Sn-Bi-based alloy, which fundamentally alters the melting point from around 250°C to below 150°C. This parameter change enables low-temperature connection while maintaining electrical conductivity and connection reliability, thereby resolving the contradiction between connection reliability and heating temperature.
Solution Approach 2:
The patent employs a low-melting-point Sn-Bi-based solder that can be applied as a paste or slurry and sintered at low temperature to form reliable connections. This approach replaces expensive and complex high-temperature soldering processes with a simpler, lower-cost low-temperature sintering process, achieving both cost reduction and reliable connection.
2Reliability
If high heating temperature is used to connect solar cell electrodes and wiring substrate wires, then electrical connection is achieved, but thermal expansion difference causes stress and reduces connection reliability
Solution Approach 1:
By changing the solder material to Sn-Bi-based alloy with melting point below 150°C, the patent enables connection at temperatures that minimize thermal expansion differences between the solar cell substrate and wiring substrate. This parameter change directly reduces thermal stress while maintaining connection reliability.
3Temperature
If ACF (Anisotropic Conductive Film) is used to connect solar cell electrodes and wiring substrate wires, then connection is achieved at low temperature, but high electrical resistance reduces Fill Factor and electric characteristics
Solution Approach 1:
The patent replaces expensive ACF with a low-cost Sn-Bi-based solder paste or slurry that can be screen-printed or deposited directly onto the wiring substrate or solar cell electrodes. This substitution achieves both low-temperature connection and low electrical resistance, improving Fill Factor and overall electric characteristics.
Solution Approach 2:
The patent replaces the mechanical compression bonding mechanism of ACF with a metallurgical bonding mechanism using sintered Sn-Bi-based solder. This substitution creates direct metal-to-metal contact with low contact resistance, significantly improving electrical characteristics while maintaining low connection temperature.
4Loss of substance
If silicon substrates are made thinner to reduce raw material cost, then material cost is reduced, but cell cracking occurs during wiring operations
Solution Approach 1:
The patent changes the connection temperature parameter from high (250°C) to low (below 150°C), which eliminates thermal stress and mechanical stress during the connection process. This allows thin silicon substrates to be used without cracking during wiring operations, achieving both cost reduction and maintained strength.
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 approach enables reliable, low-cost electrical connections between solar cell electrodes and wiring substrates at lower temperatures, reducing the risk of cracking and improving electric characteristics, such as Fill Factor (F.F.), while eliminating the need for high-temperature soldering and expensive ACF.
Implementation Method 1
uses a conductive adhesive agent, such as an Sn—Bi-based solder, with a low melting point and low electric resistivity
Implementation Method 2
an adhesive agent for adhering the solar cell and the wiring substrate to each other
Data Source
AI summary
The present invention provides a solar battery including a solar cell (100); a wiring substrate (200) having a wire (109, 110) to be electrically connected to an electrode (106, 107) provided in the solar cell (100); and an adhesive agent for adhering the solar cell (100) and the wiring substrate (200) to each other. The present invention also provides a method for manufacturing the solar battery, a method for manufacturing a solar cell module using the solar battery, and the solar cell module.