Research on Coating Formation Mechanism of a High-Temperature-Resistant Organic Solderability Preservative and the Coating Performance in PCB

To overcome lead-free high temperature reflow process and obtain satisfactory solder joints on printed circuit board, the key issue is to generate a High-Temperature-Resistant Organic Solderability Preservative （HT-OSP） coating on the surface of copper solder pads. Selecting C₁₄H₁₀C_l2N₂ as a coating formation agent, a HT-OSP coating is formed on copper surface. Theoretical calculations combined with comparative experiments, coating formation mechanism of C₁₄H₁₀Cl₂N₂ molecules reacting with copper atoms generating the HT-OSP coating is investigated. Based on the density functional theory in quantum chemistry, the complexation reactions between C₁₄H₁₀Cl₂N₂ molecules and cuprous ions are simulated. The typical functional groups in the HT-OSP coating are characterized by infrared spectroscopy. The valences of copper element in the HT-OSP coating are tested by X-ray photoelectron spectroscopy. The influence of copper ions on forming HT-OSP coating is analyzed by designing comparative experiments. The results indicate that the mechanism of generating HT-OSP coating is as follows: C₁₄H₁₀Cl₂N₂ molecules react with copper atoms generating HT-OSP coating deposition on copper layer surface. Copper ions promote the HT-OSP coating growth by complexation reaction. Moreover, the decomposition temperature of the HT-OSP coating is up to 531 °C. The copper layer protected by the HT-OSP coating is not oxidized after 180 days in the atmospheric environment. It is proved that the HT-OSP coating possesses excellent antioxidant and heat resistance.