Electroless Copper Deposition
The next step is to add a thin layer of metal in the hole. The problem is that the hole has nonconductive dielectric layers. To metalize the nonconductive layers the board is immersed in a bath that coats all surfaces with a very thin layer of copper. The electorless copper bath achieves this process chemically but coats all surfaces that are exposed to the bath. Dielectric and metal surface are coated. <