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Let's look at the top layer information first using the ViewMate Gerber viewer program.

The first thing you notice is that the artwork is displayed significantly offset from the origin at the lower left corner of the screen. Don't panic; this is normal. The offset is caused by the placement of your layout with respect to the maximum size of your program's workspace. Also, it's not uncommon to find the artwork inverted about the X or Y axis. What IS important is that the displayed artwork "looks" like what you designed. Look for things like missing pads and tracks.

Two common problems can be spotted when viewing Gerber files. One is evident when the tracks look like "stick figures" and the pads look like dots. This occurs when the aperture information is not present in the Gerber file. All of the tracks and pads are read-in with a default width, usually 0 mils. You will need to go back and fix your file output to correct this problem. Usually, this is the result of selecting RS-274D instead of RS-274X and not supplying the associated aperture file. The other common problem is evident when the tracks and pads look huge and overlap one another. This is caused by a specification error in the leading/trailing zeros selection or an incorrect selection in the m.n format information. Using most viewer programs, you can measure the space between pads and see if they make sense (e.g., 0.1 in. between DIP pads). Also, select a track and make sure that its associated D code is correct.  

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