Fusing the tin-lead coating
11 The tin-lead coating on the surface of the copper printed circuit pattern is very porous and is easily oxidized. To protect it, the panels are passed through a "reflow" oven or hot oil bath which causes the tin-lead to melt, or reflow, into a shiny surface.
Sealing, stenciling, and cutting the panels
12 Each panel is sealed with epoxy to protect the circuits from being damaged while components are being attached. Instructions and other markings are stenciled onto the boards.
13 The panels are then cut into individual boards and the edges are smoothed.
Read more: http://www.madehow.com/Volume-2/Printed-Circuit-Board.html#ixzz3yzklsMzY