Step 6: Silk Screen
A silk screen is all the printing, information and component outlines shown on the top of the PCB. This is useful for stuffing components and later for troubleshooting. Probably you will do parts of this procedure in conjunction with the traces but I made it a separate step.
So we have to create an image for the silk screen.
Eagle: In the board editor, there is a little icon called Display (Show/Hide Layers). Click on it, select <None> then click on (highlight) these layers:
Now, just the silk screen and pads should be displayed.
<Browse> Select the directory and file name that you want.
Click <OK> to export as image.
Again you will notice that the stuff you want printed is in white and needs to be black so again we need to Invert. So what isn’t so obvious is that since the silk screen goes on the opposite side of the traces we need to flip the image. Here’s my procedure.
Make Invert and Flip:
Open Image with PhotoShopElements
<Image><Crop> Crop <Check> Crop the image to contain the outline and dimensions
See picture. Note that the printing is mirrored.
Use the same procedure as with traces.
Mark the blank printer sheet.
Print the silk screen.
Cut the vinyl.
Attach it to the printed page.
Stick the paper/vinyl in paper feed.
Cut the paper/vinyl leaving about ¼” border around the silk outline.
Aligning the silk screen with the traces:
I know when I cut copperclad and tape it to traces it is far from perfect. This makes it a little harder to aligning the silk screen with the traces.
So what I do is take the etched PCB, find a couple of pads on opposite sides of the PCB and drill them out.
I find the same holes on the paper/vinyl and drill them out or open them with an Xacto.
Next I take a couple of cut off resistor leads, insert them into the two holes and insert them into the matching holes in the silk screen. See picture.
Now the silk screen should be properly aligned with the PCB.
Scotch tape the PCB to the silk screen.
Remove the resistor leads and trim the paper/vinyl.
Warm up the laminator and follow the same procedure as with traces.
Be careful, the copper side gets hot. Use gloves if you want.
The silk screen came out pretty good. The backside of copperclad is not the best surface to be printing on. I’m not sure how to keep the silk screen from wearing off. I imagine there’s some good spray on clear sealant?
TIP: I’ve been doing another thing, I didn’t mention. In Photoshop Elements, I open a blank file and copy the traces and the silk to it. Depending on the size, you can have multiple copies of each. With this file you can print the traces and the silk at the same time and even make multiple copies if you’re planning to make more than one PCB.
Conclusion: I like this method of making PCBs with my laminator and vinyl stickers. They seem to be more consistent and it apparently will do much smaller traces then my old glossy paper & iron method.