Interconnection

• Drilling of holes using the design data for size and location is the start of the interconnect process.  Drilling provides the mechanical opening that contacts or clears internal features.  In the case of many internal layers (multilayer) the contact points are now the avenue of electrical communication.
• Hole Clean is the process (usually chemical) that removes any internal debris from the internal connection.  
• Depending on the materials and specifications the walls can be simply cleaned (Desmear) or aggressively attacked (Etchback) such that the inner copper features actually protrude into the drill hole opening.