How to make a PCB

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Published on 18 Jun 2020 - Updated on 05 Dec 2020

When number of layer is greater than two Printed Circuit Boards (PCB) are made by stacking multiples cores and prepreg sheets. Internal layers are manufactured first then outer layers are done at the end.

Process

Step 1 : Core

PCB Core “Core” sheets are composed by an epoxy resin with a copper sheet on each side. Usually PCB manufacturer receive it already assembled with a photosensitive resin applied on each copper side.

Step 2 : Photomask

PCB Core light coating UV light with photo film are used to print traces and pads on photosensitive resin. Photosensitive resin gets hard when it receives UV light. This process protects copper areas where traces are located.

Step 3 : Traces printing

PCB traces printing Non protected copper is dissolved by a chemical bath. Then another bath removes remaining resins.

Step 4 : Repeat for each core

PCB etching Step one, two and three are repeated to prepare each core. Two times for a six layers PCB, Three times for eight layers PCB, etc..

Step 5 : Core stacking

PCB Core stacking All cores are stacked with a prepreg isolating sheet between each. The “Prepreg” sheet is made of multiple fiberglass layers glued with resin. The two external layers are created by assembling a copper sheet on top of “prepreg”.

Step 6 : Glue all layers

PCB Glueing All assembled layers are compressed together at high temperature. This allows to harden resin and to glue all layers.

Step 7 : Drill vias

PCB via drilling Vias are drilled using a laser beam or a drilling machine depending on hole size.

Step 8 : Vias plating

PCB via plating To allow via to conduct between all layers, copper is added inside via holes using electrolysis process. During this step, external layers copper thickness increase also.