Solder Mask Over Bare Copper

Solder mask over bare copper, silk screen one side only... 

Before the widespread use of solder mask, a primary method for protecting copper circuitry was to electroplate a coating of tin or tin-lead on the copper. After component insertion, the tin plating could be liquefied with oven or vapor-phase reflow to form solderjoints.The use of solder mask over bare copper to take advantage of surface mount, wave soldering, and mixed assembly restricted the use of tin plate finishing. For simple technology product, tin or tin-lead plate and reflow remains a viable fabrication and assembly method. 

PTH reliability and on the reliability of the solder joints made to these pads. Common metal finishes for solder-mask-over-bare-copper (SMOBC) boards inclnde hot-air solder leveling (HAST or HAL), organic-coated copper (OCC), and electroless NiAn. Galvanically plated CuNiAu and CuNiSn made by another processing route are also available.These finishes provide a solderable finish for later printed circuit assembly. The pros and cons of the various finishes are discussed in turn. 

SMOBc Solder mask over bare copper. A method of fabricating a printed wiring board which results in the final metallization being copper with no other protective metal but the non-soldered areas are coated by a solder resist, exposing only the component terminal areas. This eliminates tin-lead under the solder mask. 

Copper Circuitry. A large majority of panels produced have solder mask coated over bare copper (SMOBC). The goals of the surface preparation process are to remove all unwanted oxides and contaminants from the copper and to impart a microroughness or tooth to the surface, and to leave a clean, dry surface for coating. 

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