Surface treatment chemicals for PWBs
![OSP](https://kagaku.shikoku.co.jp/wp/wp-content/themes/shikoku/assets/img/products/pwb/preflux-about/plfxabout_tab1_01.png)
What's OSP
OSP coating protects copper surface from oxidation to keep excellent solderability and plays a prominent role in component mounting process.
Basic information
Components
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Imidazole derivative
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Copper ion
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Organic acid
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Water
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OSP coating
OSP is an immersion coating process.
After 30 to 90 sec immersion, 0.2 to 0.3um thickness OSP coating forms on copper surface.
![OSP is an immersion coating process.](https://kagaku.shikoku.co.jp/wp/wp-content/themes/shikoku/assets/img/products/pwb/preflux-about/en/plfxabout_tab1_02.png)
Functions, Demand characteristics
Functions of OSP
By Keeping excellent solderability, OSP acts as a bridge between PWB manufactures and assembly manufactures.
![By Keeping excellent solderability, OSP acts as a bridge between PWB manufactures and assembly manufactures.](https://kagaku.shikoku.co.jp/wp/wp-content/themes/shikoku/assets/img/products/pwb/preflux-about/en/plfxabout_tab2_01.png)
Demand characteristics of OSP (Example)
Excellent solderability
![Good example](https://kagaku.shikoku.co.jp/wp/wp-content/themes/shikoku/assets/img/products/pwb/preflux-about/en/plfxabout_tab2_02.png)
Good example
Copper surface covered by solder completely
Copper surface covered by solder completely
![Bad example](https://kagaku.shikoku.co.jp/wp/wp-content/themes/shikoku/assets/img/products/pwb/preflux-about/en/plfxabout_tab2_03.png)
Bad example
Exposed copper
Exposed copper
OSP coating mechanism / OSP line
OSP coating forming mechanism (Theory)
Excellent solderability
![Excellent solderability](https://kagaku.shikoku.co.jp/wp/wp-content/themes/shikoku/assets/img/products/pwb/preflux-about/en/plfxabout_tab3_01.png)
Typical OSP process
![Typical OSP process](https://kagaku.shikoku.co.jp/wp/wp-content/themes/shikoku/assets/img/products/pwb/preflux-about/en/plfxabout_tab3_02.png)