Page 159 - Make Your Own PCBs with EAGLE from Schematic Designs to Finished Boards

CHAPTER 6

Printed Circuit Board Fabrication

A t the end of Chapter 5, we had a finished board layout. We now need to use that to generate

the files that can be sent to a PCB fabrication company that will in due course send us back
some real PCBs.

The CAM processor is the EAGLE module that converts the layers in the EAGLE PCB design and
produces the industry standard files required to fabricate the PCBs. This chapter explains this process
and shows you how to produce such files using the example sound meter project developed in

Chapters 4 and 5.
Although you can create your own PCBs using photosensitive PCBs and photo etching, it can be a
messy and tricky business. It is also relatively expensive because the developer and etchant
chemicals do not last. They are also toxic and difficult to dispose off because you cannot simply wash
them down the drain. Because you can have a double-sided silk-screened drilled PCB made by a

fabrication service for a dollar or two per board, even for runs of 10 or fewer boards, unless you are
in a real hurry or just enjoy the process, there is little point in making the boards yourself.
Having said that, later in this chapter we will look at photoetching your own PCBs.

Gerber Files

Although some PCB fabrication services will accept EAGLE design files directly, most require you
to produce a set of what are called Gerber files. These files are an industry standard for PCB
fabrication. You will normally be required to produce seven files.

Table 6-1 shows the files that you should submit. Each of the files has a different extension that
indicates its contents.

TABLE 6-1 Gerber File Types for CAM