PV module solder paste is a crucial material primarily used for soldering components on conductive tabs and tinning on tin reservoirs in PV junction boxes. With technological advancements, components have become highly integrated, and tin reservoirs are generally replaced by tin foils. Therefore, in modern processes, most manufacturers use medium-temperature solder paste to fix tin foils, and complete the final soldering of pre-placed tin foils through a secondary reflow production process.

I. Composition and Formula Design

The formula design of solder paste closely follows the technological iterations of the PV industry, continuously optimizing the alloy and flux systems.

• Alloy System: Early on, depending on environmental requirements, it was divided into conventional leaded Sn63/Pb37 and lead-free Sn99/Ag0.3/Cu0.7 alloys. With the integration of components, to meet the temperature requirements of the secondary reflow process, the mainstream has shifted to using medium-temperature Sn/Bi/Ag0.3 alloy to fix tin foils. Among them, the 0.3% silver content ensures the reliability of soldering strength while effectively controlling material costs.
• Flux System: Utilizing an advanced 0-halogen formula, while ensuring reliable soldering to the nickel-plated layer, it can effectively control corrosion to conductive tabs, making the long-term electrical performance of the product more stable and reliable.

II. Technical Advantages and Performance Indicators

Our PV module solder paste possesses excellent process performance and post-solder quality:

• Stable Printing Performance: The solder paste viscosity is 100±20 pa.s, and the thixotropic index is 0.5±0.05, ensuring high consistency in dotting volume (CV < 5%).
• Excellent Post-Solder Residues: The residues are colorless and transparent, with outstanding yellowing resistance, ensuring the long-term aesthetic appearance of the module.
• Superior Soldering Quality: Solder joints are full, glossy, and have excellent tin coverage, forming reliable electrical and mechanical connections.

III. Process Control Flow

From raw materials to finished products, we implement strict quality control throughout the entire chain, ensuring a high degree of consistency in product performance:

Process Flow: Incoming material inspection → Warehouse storage → Solder paste ingredient preparation → Solder paste synthesis → Storage → Grinding → Storage → Thawing → Solder paste testing → Solder paste ingredient preparation → Mixing and synthesis → Finished product testing → Packaging → Storage → Outgoing inspection.

IV. Product Models and Alloy Systems

Representative Product Models

• ES330
• ES380-T
• B353

Main Alloy Components

• Leaded Alloy: Sn63/Pb37
• Lead-free High-Temperature Alloy: Sn99/Ag0.3/Cu0.7
• Lead-free Medium-Temperature Alloy: Sn/Bi/35/Ag0.3