Organic solderability preservative or OSP is a method for coating of printed circuit boards. It uses a water-based organic compound that selectively bonds to copper and protects the copper until soldering. Compared to the traditional HASL process, the OSP process is widely used in the electronics manufacturing industry because it does not require high-temperature treatment and significantly reduces the risk of metal corrosion, environmental impact and damage to electronic components.
The basic principle of SP to form a protective layer against oxidation and corrosion by applying a layer consisting of a mixture of organic acids and nitrogen compounds, etc.
The OSP process involves delicate steps designed to ensure the uniformity and quality of the protective layer. Although environmentally friendly and suitable for microelectronic manufacturing, the complexity of the process requires strict control of the composition and quality of the coating agent to guarantee consistent board performance.
The compounds typically used are from the azole family such as benzotriazoles, imidazoles, benzimidazoles. These adsorb on copper surfaces, by forming coordination bonds with copper atoms and form thicker films through formation of copper (I) – N–heterocycle complexes. The typical film thickness used is in the tens to hundreds of nanometers.
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editReferences
edit- Tong, K. H., M. T. Ku, K. L. Hsu, Q. Tang, C. Y. Chan, and K. W. Yee. “The Evolution of Organic Solderability Preservative (OSP) Process in PCB Application.” 2013 8th International Microsystems, Packaging, Assembly and Circuits Technology Conference (IMPACT). Institute of Electrical & Electronics Engineers (IEEE), October 2013. doi:10.1109/impact.2013.6706620.
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