As an EMC consultant, I have a constant need to review other company's PC board layouts during my design reviews. Often, I can perform the review right on the client's premises, but I also can perform the reviews remotely from the home office, which saves the client money. These board layout files are usually saved in multiple file formats using many common CAD design tools, such as Mentor, Altium and others. Obviously, purchasing PC board design software from multiple vendors is beyond my budget. Fortunately, most vendors of board design software also provide free "viewers" that will allow the display of color-coded individual or multiple layers of the traces and planes. Most will load in multiple file formats.

Here are several that I find useful. Most of these viewers are designed to run on a PC, but I found one that will run on the Mac platform, which I prefer using. To run PC software, I use the Parallels virtual environment for the Windows OS.

Gerbv  - A free open-source Gerber viewer (). This is one of my favorites and can import several different file formats. It's easy to make layers visible or hidden, pan around, and zoom in and out. Hovering over a trace will highlight it throughout the layout, which helps a lot when trying to identify the paths of individual nets.

Altium Designer () is also a favorite and is a subset of the full Designer PCB and schematic design environment. All the usual tools are available, like "home", zoom, and so forth. Layers may be hidden or visible, but it's a multi-step process to do so. Otherwise, it's very full-featured. Reads in Altium and DXP files.

PADS Viewer - Is downloadable from the Mentor web site (). This will allow you to view layout files designed using PADS2007.x or PADS 9.x. I find the mentor user interface somewhat clunky on a PC.

GC-Prevue - A free download from GraphiCode (). Allows you to view Gerber files and will read DPF, Fire 9000, NC info and HPGL files. Has plenty of easy to use tools across the toolbar.

ViewPlot - A free downloadable Gerber viewer from Roneda PCB Design Consultancy (). It will import Gerber D, Gerber 274X, HPGL, AutoCAD DXF, Excellon drill data, Bitmap or TIFF file formats.

ViewMate - Has a free version Gerber viewer () that will import Gerber, DPF, OBD++ and HPGL files.

And for the Macintosh computers:

McCAD GView - From McCAD () has a free Gerber viewer (the Lite version), but it can only read in two layers at a time. Their "Pro" version costs $195, but I found it very non-intuitive to use, preferring some of the more fully featured and easier to use free PC viewers.

So, have you used any of these viewers? Which one do you find you like the best? Have I missed any good ones? Please reply in the comments below, so others may see your thought, as well.