Explanation Solder Mask and paste mask difference

For solder mask Layers and paste mask Layers Two concepts, there are many beginners do not understand the concept of these two layers, because they do have some similarities, on their own view, tribute everyone reference:

Solder Masks Layers: That is, the solder mask layer, is the PCB board (surface patch Pads, plug-in pads, vias) outside a layer of green oil, it is to prevent the PCB over tin furnace (wave soldering), should not be tin on the place of tin, so called solder mask layer (green oil), I think as long as you see the PCB should see this layer of green oil, solder resist layer can be divided into top Layers R and bottom Layers two layer, solder layer is to expose the pad, this is what we see only the solder layer when the small circle or small square ring, Generally larger than the pad (solder surface meaning is the solder mask layer, is used to apply the green oil and other resistance welding materials, so as to prevent the solder is not needed to solder, this layer will expose all the solder pads need to be welded, and the hole will be larger than the actual pad); When generating Gerber files, you can observe solder The actual effect of Layers.

Paste Mask layers: Solder paste protective layer, is for surface-mount (SMD) components, the layer used to make steel film (sheet), and the hole on the steel film corresponds to the circuit board SMD device Solder point. When soldering on surface mount (SMD) devices, first, the steel film cover on the circuit board (and the actual pad corresponding), and then the solder paste, with scraping the excess solder paste scraping, remove the steel film, so that the SMD device solder pad added solder paste, and then affixed to the SMD device paste on the top (manual or SMT machine), Finally, through the reflow soldering machine to complete the SMD device welding. Usually the size of the aperture on the steel film will be smaller than the actual welding circuit board, by specifying an extension rule to enlarge or reduce the solder paste protective layer. For different pads of different requirements, can also be set in the solder paste protective layer of multiple rules, the system also provides 2 solder paste protective layer, respectively, the top layer solder paste protective layer (top Paste) and the bottom solder paste protective layer (Bottom Paste).