For those designs that require more than one layer, double-sided printing is the way to go. A double sided print is essentially just two separate aligned prints, with a drilling and via-filling step in between.
To print a double sided board, you will need vias or through-holes in your design and your board. These serve two purposes:
- To electrically connect one side of the board to the other
- To perform registration between the sides - making sure that the layers are superimposed correctly.
Unless you are using vias that already exist in the substrate (in templates, for example), you will need to drill the through holes and vias yourself. We use a rotary tool (such as a Dremel) to drill our prototype PCBs in-house. A rotary tool collet and a PCB drill bit set are inexpensive and will help you drill a variety of sizes for vias and through-hole pads.
1. Print and Bake the First Layer
We suggest printing the least complex layer first. If your bottom layer is just routing to vias, print this one first!
Just load gerber file (.GTL, .GBL or the correct .GBR file) and proceed as usual. Make sure to include the drill locations as well, which are typically in a .txt file.
For bare boards, use the standard 'simple' alignment procedure. If using a template, use the Aligned Print procedure.
2. Drill the Board
The next step is to create the vias, through holes, and mounting holes that you'll need for your design. We use a rotary press, but there are a number of other methods that you can use, include mills and drill presses.
Have access to CNC drilling equipment? If so, we recommend performing this step first. For more information, skip down to the end of this section.
3. Fill the Vias
Before you can print the second layer, you will need to create the conductive connections between the two layers using conductive ink. To do this, do the following:
- Place masking tape or painters on the first layer, covering any holes tightly. This will prevent any leakage of ink.
- Clamp the board onto the printing platform, tape-side-down.
- Load the gerber bottom layer file (.GBL, or the correct .GBR file). The V-One software will automatically mirror the design in the x-axis.
- Perform the Pad Location Step and Probe the board.
- Now that the board has been located, we can manually fill the vias with conductive ink. Take the conductive ink dispenser in two hands, and carefully dispense conductive ink into the drilled vias.
- When all the vias are filled, wipe down the board with some paper towel to remove excess ink. Ensure that the vias are still full - if there are any gaps, touch up the via with conductive ink and repeat.
Fill vias slowly, and make sure that conductive ink goes all the way to the bottom - it's fine to spill over onto the top of the board. Take care with the nozzle, but don't be afraid to insert it fully into the drilled hole.
4. Print the Second Layer
From here, just click Print to complete the second layer. Once the print is complete, make sure there is connection between the ink on the board and in the vias.
5. Flip the Board & Clean up the Top Layer
- Remove the board from the clamps, and rotate the clamps to prepare for baking.
- Carefully remove the masking / painters tape from the first layer.
- Flip the board and rest it on the baking ledges with the wet ink facing down. Make sure that it is held snug on top of the ledges.
- If you see any ink from the via filling that has smudged, clean it up with paper towel or a Q-tip - isopropyl alcohol will help as well. Don't worry, this will not damage the baked ink.
- If necessary, touch up the vias with conductive ink to ensure good connection between the baked ink and the filled via.
6. Bake the Second Layer
All that's left to do is to click 'Bake'. After the second bake step, your double-sided board is ready for assembly and testing!
Having problems with via connection? See our troubleshooting guide for information on fixing an open circuit after breakage.
Double Sided with CNC Machining
If you have access to a CNC drill, you can reduce the risk of broken vias and misalignment that occurs with hand-drilling. Just make the following adjustments to the procedure.
- Drill the holes in the substrate first, before printing the first layer! This will reduce the risk of breaking a connection later on.
- Fill and bake vias second (also before printing the first layer)!
Using this adjusted procedure will front-load the risky aspects of double-sided printing, namely drilling and filling vias, so you don't need to worry about printing two layers before discovering a problem.