From Ece

Just like an editor proofreading a writing assignment, all schematics and boards should be reviewed by someone other than the designer before they are sent off for fabrication. Even with careful checking, most commercial PCBs go through at least one more revision before they are correct - there are a LOT of opportunities for error.

At this point, it is assumed that you are familiar with PCB Design & Assembly. You should know how to edit your schematic/board and how to make the layout tool output manufacturing files (Gerber & drill).

Necessary files for schematic/board review

Even before you create manufacturing files, have someone look over your schematic and board files. The reviewer will need these:

• Schematic file - *.sch
• Board file - *.brd
• Library file(s) for any custom parts that you created - *.lbr

TODO: Someone fill in the file types for an Orcad design

What kind of things should the reviewer look for in the schematic?

• Sufficient decoupling caps
• Power supply protection - fuses, in-rush limiter circuits, etc.
• Mistakes specific to the design
• TODO : Someone add to this list, what would you check for?

The designer should have run an Electrical Rule Check (ERC) in the schematic tool. This will do a good job of finding things like unconnected input pins, two output pins connected together, etc.

What kind of things should the reviewer look for in the board layout?

• Good ground and power distribution
• Decoupling caps placed close to their respective IC
• Lots of distance around clock traces and other high speed traces (to avoid crosstalk)
• Components oriented the right way - i.e. no right angle connectors pointing into the center of the board

Again, the designer should have run a Design Rule Check (DRC) in the layout tool. In Eagle, I run the 'Clearances' section of the DRC with all the values set to 6 mil. This is the minimum separation between two elements that the board house requires.

Necessary info to order a board

The board vendors require 5 Gerber files and 1 Excellon drill file to fabricate a 2 layer board. These files are the output of your PCB layout tool.

If you are using Eagle, here are the 6 files that the CAM processor will output.

-------------------------------------------------------
File   Layers               Meaning
-------------------------------------------------------
*.cmp  Top, Via, Pad        Component side copper
*.sol  Bot, Via, Pad        Solder side copper
*.plc  tPl, Dim, tName,     Silkscreen comp. side
*.stc  tStop                Solder stop mask comp. side
*.sts  bStop                Solder stop mask sold. side
*.drd  Drills, Holes        Drill data for NC drill st.
-------------------------------------------------------

If you are using Orcad, here are the 6 files that Post processing will output.

-------------------------------------------------------
File   Meaning
-------------------------------------------------------
*.top  Component side copper
*.bot  Solder side copper
*.sst  Silkscreen comp. side
*.smt  Solder stop mask comp. side
*.smb  Solder stop mask sold. side
*.drd  Drill data for NC drill st.
-------------------------------------------------------

Preview the Gerber files

This is optional, but I found it helpful to preview the Gerber files to make sure that each file has the correct design info in it.

• Viewmate from Pentalogix is a freeware Gerber viewer that has worked fine for me.

Don't forget: How many and which vendor?

The only other info needed is how many boards and which board house to use. Refer back to PCB Design & Assembly#PCB Fab Services

NOTE: I advise against ordering only one (1) board; give yourself a backup.