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In the next step we'll bring in the bottom (solder) layer and view it along with the previous top layer information.

Again, we see that the top artwork is present even though we added the bottom layer information. Also, the bottom layer artwork lines-up with the top layer artwork. Note: The dimension and text data are removed by PCB Milling prior to board fabrication.

At this step the most important thing to look for is any CHANGE in the artwork as the second layer is loaded. For example, if the track width for the top layer tracks changes when the bottom layer is brought in, a problem exists in the aperture information. The newly imported layer's aperture information most likely has overwritten the previous layer's D code information. Generally, this is caused by generating Gerber information for one layer "after the fact." If you modified the bottom layer artwork and then generated a Gerber file for ONLY the bottom layer, it's quite possible that the D codes were overwritten from their previous values. It is important to generate Gerber files and aperture information for ALL active layers at the same time.

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