Adding a decorative graphic
In this chapter, I’ll show you how to decorate your PCB with graphics on either the top or the bottom silkscreen layer. Decorating a PCB is usually the last thing you want to do before you export the Gerber files and send them to manufacturing. The decorative graphic could be a logo or some other symbol that you would like to show on your PCB. You can place the graphic on the top or the bottom silkscreen layer. For this project, I will take my logo graphic, convert it into a footprint (that has no pads) and then place it onto the PCB.
The way that KiCad works with graphics is by using a utility that converts a graphical file into a footprint. The utility produces a footprint without any pins or any holes or vias or any other elements other than the contents of the silkscreen, which you can place on the PCB.
The process starts with the image. The tool that Kicad provides to manipulate images is minimal in terms of functionality.
Here’s my logo, an image in PNG format:
We will start with this PNG image.
It is around 2000 pixels in width, which is too large to fit on this PCB without resizing.
Step number one is to resize the image as big as your PCB is going to be. I’m going to go back into PCB new and do a quick measurement. I’m going to put my cursor up in the top corner, top left corner, hit the space bar to zero the dimensions and then move across to the right corner. You can see that in the X horizontal axis I’ve got 29.08 millimeters, so 29.08 millimeters. If I go down I have 22 millimeters. You should write these values down. That is 22.7 millimeters in the Y axis and 29.21 in the X axis. I can close that now.
The tool I’ll be using to do the conversion of the png image into a footprint is Bitmap2 component. Let’s open up bitmap2 component and go to the black and white picture tab and load the bitmap. You should go into desktop, project folder, this is a latest image. Looks a bit big, it was 72dpi, so I can change that to let’s say 300. I’m changing the dpi, you can see that the size updates. This is a good way to control how big your image eventually will look on the PCB. I know that the dimensions of my PCB in width is 29.21 millimeters, so looks like this. It is still a bit too wide, so I will increase that maybe to 400, 500, I will increase them to– I’m going to go down to below 29 millimeters, so make that a 1000. No, a bit too much, maybe 800. Yes, 850, okay.
You need to keep track of your other side as well, 850. I think these settings at 850 dots per inch will produce an image, a footprint that is 22.4 millimeters in width and 14.9 millimeters in height. That should comfortably fit inside my PCB. Next I want to leave this as normal. Normal will produce a graphic with a wide silkscreen ink on the PCB instead of having a wide silkscreen ink everywhere outside the graphic itself. What I want is white on green or purple for Oshpack instead of purple on white. I hope that makes sense but you can see what happens if you choose negative.
Now, much that you have received the PCB from Oshpack, the black ink here will actually be purple since the PCB color from Oshpack is purple and then everything else around it is going to be white. I would rather go with the white marking for my logo. I will just leave it like that and everything else around it is going to be a default purple for the PCB, so the mask. You can play around with the threshold value but I find that about 80% is fine, so this basically tells you which part is white and which part is black. I’ve got black and white, anything above that reverses the colors. I will leave it at about 80%.
The format is PCB new since this is my target tool. All right, so I will export this and I will save the new graphic as a footprint in a new library inside my project folder. I go back to my project folder and then in here I’d like to create a new folder. I will call it something like graphics.pretty. Remember that the pretty extension is important because it denotes a library for footprints. Make sure you’ve got .pretty in here. Drill inside your new library folder and give your new footprint a name. Let’s call it T-explore logo and save.
We’re done with the tool. We got a new library for this footprint. We can now go into the PCBnew app. The first thing to do is to import the new library, just like we’ve done in the past with the custom component footprint. We go into preferences, then I use the footprint libraries manager and I will use the, append with wizard option to drill and find my new footprint library. That’s in here somewhere. There you go, graphics.pretty is what I’m looking for.
Next, it’s looked inside. It’s found that it contains footprints that are good. I’m going to add this to the current project only. I didn’t add it to the global projects, globally accessible because the way that I have customized the dimensions for this graphic really makes sense only for this current PCB. I’m going to click okay to finish.
Now, I need to add this new footprint. I can click on this button here and I will just put the new footprint here. Now I will see if hopefully it’s in my library folder because sometimes actually you have to restart PCBnew in order for it to load the library contents you’ve just added. Let’s see if it’s somewhere here. You should probably search for logo. There is T-explore logo, good. Okay and here it is.
Here is a logo that I’ve just added. I’m just going to put the logo here and what I want to do is to edit its location. I want to put this in the bottom side. Get the properties for the logo and choose site from top to bottom and use an M key to move it in place. Around here would be okay. I can also remove the text that I added earlier since I no longer need it. Just remove that, gone. All right. Refresh.
I’ll actually move my logo a little bit higher, so around here and that looks okay. Let’s check it out in the 3D view. There it is. There’s the nice new graphic. Actually I should probably flip it, so edit these properties again and I want to rotate it by 180 degrees. I hope that would do the trick. Check out 3D viewer, just want to ease the orientation to be appropriate. This is the top, that the bottom. The orientation now is good, top and bottom. Nice. Don’t forget to save your project. Let’s refresh the drawings and there you have it. You can now decorate your PCBs with nice graphics. You can now take this PCB if you like and upload it to Oshpack and manufacture it and your graphic will be honored.Back to top