Eagle pcb to image for toner transfer (a lil tutorial)
After trying to get it done properly and making lots of silly mistakes I finally have it figured out, so read here if you want to make an image file for toner transfer method of the PCB you created in Eagle or maybe another PCB cad program. I had some problems with the tracks not being the size and the holes where smaller or larger and it was a nightmare for a while.
Also this works very good if your PCB doe not takes much space and you want to print it multiple times on a sheet of photo paper. There is no point in wasting a photopaper sheet with one copper layer printed if you can print out 5 or more of them on the same page.
I use Eagle and Gimp (freeware Photoshop like software) for image processing and layout.
1.- In Eagle open the .brd and set the layers to Bottom, Pads, Vias. I don't use Dimensions layer because it draws holes of TO220 package components.
Check "monochrome", choose resolution (default 150). I usually put there 300dpi and this must match the dpi of the file you will create in Gimp, just remember that.
Click "Browse" chose your folder and filename and extension, I usually go with .png
3.- Open the image in Gimp, you will see the image is all black but the vias.
Filters>Colors>ValueInvert will fix it.
Now for toner transfer we must flip the image Horizontally and Vertically.
4.- If the board does not have an outline and you want one then read here, else go to 5.
An easy way to make some custom outline around the PCB is to grab with the mouse the rulers and drag them into the image, this will drag alignment guide lines into the image and arrange them so that you can use them to make quick and straight lines.
Use Pencil tool, set brush to "Circle (03)" or any you like.
Click where your outline will begin then press and hold SHIFT key and a line will appear between the first point you have set and wherever the mouse is, if you have used helping lines then the pencil line will snap on the intersections, complete the outline. Save.
5.- Use "Select Regions by Color" tool, its the one with 3 color squares and a finger pointing at them.
Click on any black part of your image. Only the black color will be selected and all of your design is in black so everything is selected.
Now here is where the dpi number you have used to export the image from eagle comes at hand to get everything exactly as you want it to be.
Open Advanced options. Input here the dpi you have selected in Eagle, if you have used 600dpi then input 600 into "X resolution" and "Y resolution".
Color Space> Grayscale
Fill With> White
A new file must have created with the dpi you need and with a white background.
7.- In the new file window select the zoom you need.
View>Zoom>1:4 (works for me).
Select the "Move layers & selections" tool, its the one that looks like crosshairs, shortcut letter "M".
If you want you can drag some guides from the rulers into the page and this way limit the page to the shortest printing margins, which I think are
Left: 6.4 mm (0.25 in.)
Right: 6.4 mm (0.25 in.)
Top: 1.0 mm (0.04 in.)
Bottom: 11.7 mm (0.46 in.)
8.- Once you are ready to lay out the image you have in the clipboard (remember you did Edit>Copy) just Ctrl+V and an image of your design will be pasted, using the "Move layers & selections" tool drag it to the position you want and let go, it will snap to the guide lines so it pays using them as they speed up alignment. Once the image is in place point the cursor on an empty area and the cursor will have an anchor on it, click on white spot and your image will be anchored and you wont be able to move it anymore (or so I think).
If you messed up anything just Ctrl+Z to undo changes.
9.-Repeat the step 8 until u have used all available space, if you need your design to be rotated then switch back to the original image and
Image>Transform>Rotate to the position you need. Copy it and go paste it in the US-Legal sheet.
10.- Now print your copper layout on a regular paper and triple check everything is ok. Use a component with many legs, any IC will do and see if it fits, it must do so perfectly.
If it is then check once more and then go print on a photo paper and on with the toner transfer.
Hopefully you will find it easy and useful.
I usually go to CorelDraw9 and simply import the image I have created with the above mentioned method,"Import" it into a new Corel design. Then I do PublishPDF and grab that file for printing on some nice laser printer which I do not have myself.
Eagle is a pain to learn sometimes but it does have just about everything you need , including being able to quickly and easily print for toner transfer. Finding how to do stuff is often another matter.
The rescaling is to allow for differences between *printers* - not because there's any varience in the program output. Printers differ and some print longer or wider than others for the same file. I've used lasers that all print a slightly different ( ranging from 1.02 - 1.16) size from the print command. The variance can be enough to cause problems on db25's for example.
I do double sided with eagle by drilling and outline cutting the boards *first* using the cnc ulp to produce the gcode. Then I print the layers, scaled to be accurate and then holding them up to the light, align transfer and etch. Works well and quite fast...