LED Circuit Board Christmas Tree Ornament

This Christmas, I decided to make Christmas ornaments to give to my friends and family. I've been learning KiCad this year, so I decided to make the ornaments out of circuit boards. I made about 20-25 of these ornaments. The ornament is a circuit board shaped like a Christmas tree. The ornament has candy canes on the silkscreen, ornaments made out of exposed copper, garlands made out of resistors, and LEDs to represent the lights on the tree. The LEDs I used slowly change color, giving the tree a bit of life. The ornament has a hole at the top for hanging it on your tree with a string. There is a Micro USB connector on the back, so that you can use an ordinary phone charger to power the LEDs.

This Instructable assumes you already know how to solder, so if you don't, you should learn that first. This Instructable does not require any special skills other than soldering.

Note: This Instructable is sponsored by JLCPCB. They offer PCBs for as little as $2. (Although for this ornament, I recommend the ENIG finish, which is more expensive.)

Step 1: Materials

For each ornament, you need the following materials:

• Circuit board. For information on ordering the circuit board, see step 3.
• 1/8 watt, 1k Ohm resistors. Quantity 14. Resistor should be about 3.3-3.6 mm long. Digi-Key part number CF18JT1K00CT-ND.

• 3mm color-changing LEDs. Quantity 14. SparkFun part number COM-11448. Digi-Key part number 1568-1196-ND.
• USB Micro B receptacle. Quantity 1. Digi-Key part number 732-5958-1-ND.
• 3.3µF 0805 ceramic capacitors. Quantity 3. Digi-Key part number 1276-6461-1-ND.
• A short length of string to hang the ornament. I used Hemptique red cord.
• A USB charger and a USB cable that terminates in a Micro B plug. For the ornaments I gave as gifts, I used Digi-Key part number 993-1293-ND, which is a USB charger with a built-in cable. For my own tree, which is white, on which I hung four ornaments, I used this four-port USB charger and these 6-foot white cables.

Step 2: Tools

You'll need the following tools:

• Tweezers. I used Vetus curved tweezers.
• Scotch tape.
• Flush cutters. I used these.
• Soldering iron with screwdriver tip. I used a Weller WLC-100.
• Conical tip for soldering iron. I used Weller ST7.
• Solder. I used MG Chemicals lead-free no-clean 0.032" solder.
• Thin solder. I used lead-free no-clean 0.02" solder.
• A clean, smooth work surface that won't scratch the PCB. I used this silicone mat.

You should use the screwdriver tip and the 0.032" solder, unless the step specifically mentions otherwise.

Step 3: Order the Boards

I had my boards manufactured in China by JLCPCB. The full instructions for ordering from JLCPCB are here, but I'll go over the basics below.

Start by downloading the file TreeOrnament.zip which is attached to this step.

Then go to https://jlcpcb.com/quote and log in or create an account.

Next, click the "Add your gerber file" button, and specify the copy of TreeOrnament.zip that you downloaded previously.

Unfortunately, JLCPCB doesn't automatically fill out the dimensions from the Gerber files. So, I manually put in the dimensions of 80mm x 99mm. You should leave "Layers" set at "2", and you can set "PCB Qty" to the number of boards you'd like to order. (You might as well get at least 10 boards, because it doesn't seem to be any cheaper to get only 5. The only difference would be that the shipping might cost a little less for 5.) Set "PCB Thickness" to "1.0", and leave "PCB Color" set as "Green" (unless, for some reason, you want a different color of tree). I set the "Surface Finish" to "ENIG-RoHS". The other surface finishes are cheaper, but I haven't tried them, and I don't know if they will look as good. Leave "Copper Weight" set at "1.0", and leave "Gold Fingers" set at "No". You can leave "Material Details" set as-is, and leave "Panel by JLCPCB" set to "No".

Now click the blue "Save to Cart" button on the right side of the screen. (You might need to scroll back up to see it.)

At this point, you can use the "Gerber Viewer" link to look at the board if you like, to make sure it was uploaded successfully. When you are happy, click the "Checkout securely" button. It should be straightforward to check out from there.

At the time of this writing, ordering 10 copies of the TreeOrnament board with the ENIG finish (which is what I recommend) costs $20, and shipping to the US via DHL costs $17.11. (However, shipping is free on your first order.)

The circuit board design is open source (CC-BY-SA 4.0), and if you'd like to modify it, the KiCad source files are available in this github repository.

Step 4: Solder on the Surface-mount Capacitors

On the back of the ornament, there are three pairs of surface-mount pads for attaching decoupling capacitors. I solder them like this:

1. Place the soldering iron on one of the pads.
2. Touch the solder to the pad, to get a nice blob of melted solder on the pad.
3. With the soldering iron still in place, keeping the solder molten, use the tweezers to position the capacitor in the correct position.
4. Remove the soldering iron. The capacitor should now be connected at one end.
5. Solder the other end of the capacitor, so that it is fully connected.

Step 5: Tape USB Receptacle in Place

Insert the USB receptacle into the back of the board, and then use Scotch tape to hold it in place.

Step 6: Solder the USB Receptacle

Solder the USB receptacle. You need to solder the two large pins on either side, and you also need to solder two of the five small pins. (Specifically, you need to solder the pins on each end of the row of three. Although you can solder all five pins if you like.) For soldering the small pins, this is where I recommend using the thin solder and the conical tip.

Once the receptacle is soldered in place, remove the Scotch tape that was holding it in place.

Step 7: Bend the Resistors

Bend the legs of the resistor at a 90 degree angle, as close to the body as possible. You can just do this by hand; no tools are needed.

Step 8: Insert the Resistors

Insert the resistor through the front of the board. Then, on the back, bend the resistor legs to hold the resistor in place.

Step 9: Solder the Resistors

On the back of the board, solder the resistors in place.

Step 10: Trim the Legs of the Resistors

Use the flush cutters to cut off the legs of the resistors after they have been soldered.

Step 11: Insert the LEDs

Insert the LEDs and bend the legs to hold them in place. The short leg of the LED goes into the square pad, and the long leg of the LED goes into the round pad.

Step 12: Solder the LEDs

On the back of the board, solder the LEDs in place.

Step 13: Trim the Legs of the LEDs

Use the flush cutters to cut off the legs of the LEDs after they have been soldered.

Step 14: Tie the String Through the Hole in the Ornament

Cut the desired length of string, and then tie it through the hole at the top of the ornament. Your ornament is now ready to hang on your tree!

Step 15: Package the Ornament As a Gift

I gave most of these ornaments as gifts. I would insert the finished ornament into an anti-static bag. Then I printed some simple instructions on an address label, and affixed the label to the bag. Then I would wrap up the anti-static bag and the USB charger with tissue paper. Then I'd insert the tissue paper into a gift bag.

Don't forget to test your ornaments before wrapping them up!