What is a 2 Layer Printed Circuit Board?

We will start with a bit of a run through of how a 2 layer printed circuit board is put together. The double-sided PCB is made of epoxy glass with copper foil on both sides of the epoxy glass. Our next step is to drill all the holes in the drill file. Then another layer of copper is added to the epoxy glass and copper. This will plate vias, component holes and traces.

A layer of plating resist is added to both sides leaving vias, component holes and traces exposed. A new layer of copper is deposited on all the exposed copper. This brings the plating resist and the new copper flush with each other. The next step is the deposit a coating of tin over the exposed copper, this tin coating protects the copper on vias, component holes and traces from being removed during the etching stage. At this stage the plating resist is removed chemically, exposing the surface copper and leaving vias, component holes and traces intact.

It is now time to remove all the copper chemically. The chemical will only remove the copper and not the copper protected by the tin/lead. Now the tin/lead is removed exposing all the traces and component pads, vias etc. The solder mask layers will be added with clearance around traces, vias etc. If a silk-screen is also required the print will be done at this stage with epoxy ink. A layer of gold, silver or solder on the copper pads will be applied to all component pads, vias etc giving the expected finish for the customer.

Here at Mint Tek Circuits we strive to produce fully functional designs. In future blogs we’ll give you some deets on common errors in customer’s data.