Homebrew PCBs

You are not missing something, you are right. The main idea with the solder resist is to stop the solder in unwanted areas. This is important especially in SMD components, excess solder can cause bridges so short circuit. Another issue is excess solder can change the impedance of  microstrip lines used in RF circuit. The reddish  color comes from mixture of yellow, magenta and black (MIS Pro MP-4 Photo Black) to make it more etch resistant and visible and after curing it becomes dark reddish. You can directly use negative image of pads but in reality enlarged version of  is used to help alignment.  
 Volkan


..... If that is it, this is awesome!  I've tried different ways of doing that and
the best I could do was a disgusting mess.






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