Print 1: Calibrate
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Whenever we use a new material with NOVA we need to calibrate it. Material calibration allows us to determine the optimal print settings for any new material/nozzle combination. In this first print exercise we will calibrate our new Black Screen Printing Ink in quadrant 1 of our FR4 board.
To get started, we’ll select the CALIBRATE workflow tile from the home screen of NOVA’s software:
Once in the Calibrate workflow, all of the prompts for us as the user will appear on the left hand side of the screen.
In the calibration setup we’re prompted to select the paste that we would like to calibrate. Using the dropdown menu, we’ll select the ink we created earlier on in our Library and then the batch we’d like to use:
Since we would like to calibrate this ink directly on our substrate we’ll need to click on the Advanced option in the bottom corner. Then select our FR4 substrate in the dropdown menu:
With all the required parameters set, we now see the option to click next in the software. Let’s click it.
In this step we’re prompted to set a grid of how many calibration attempts we would like available to us before needing to clean our board. In this case we will use a 3x4 grid, this will give us 12 attempts. We will align this pattern on our substrate in a future step. Click Next.
For this design, we don’t need to do precise alignment since we’re not trying to line up to any existing features. We will be doing a deep dive on alignment in one of the later prints, so for now we’ll do a quick overview of the alignment process.
When aligning, there are three sections; Set Pivot, Set Pivot Position, and Set Rotation.
Set Pivot: In this step we select a feature in our design to use as a point of reference for alignment. The Pivot will be the feature of our design we focus on when moving our design around on our substrate. Later, it will be used as the point we pivot our design around when adjusting rotation. It’s usually easiest to select a feature in one of the corners of our design.
Set Pivot Position: During this step we are moving our designed pattern by our selected Pivot feature to the location we want to print it on our substrate. The main focus in this step is to focus on aligning the pivot point itself, not the full design. We can use the arrow keys to move the pivot point around and can fine tune the alignment by clicking the number in the center of the movement controls to adjust the step size.
Set Rotation: Once we have the pattern aligned to the pivot point, we may need to do some rotation around this point to get the rest of the design aligned. Again, we can fine tune the rotation by clicking the number in the center of the rotation controls to adjust the step size.
Now that we’ve gone over the purpose of these steps, let's put them into practice.
As mentioned before, it’s often easiest to select a pivot feature that is in one of the corners of the design. For this design selecting the rectangle in the bottom right corner makes the most sense. To do so we’ll click on it with our mouse. Once clicked, we should see the yellow cross hair move to our selected feature.
With our pivot set, we can click on the second step Set Pivot Position. The camera will need a minute to prepare itself on the XYZ tool and then move to our substrate. It’s an important step in making sure our prints are properly aligned.
Once the camera is finished preparing, we’ll see our design as an AR overlay positioned in the center over NOVA’s print area. We’ll use the movement controls or arrows on our keyboard to move our Pivot feature over quadrant 1 of our substrate. This doesn’t need to be super precise, but we’re aiming to have it to the left and above the white gridlines in the bottom right corner of this quadrant.
Click Next once the placement looks right
Since we’re not worried about our alignment being too precise we’re also going to SKIP the Tune Alignment step.
Every time we print on NOVA we need to have an idea of what our substrate surface looks like. This is because during dispensing we’re actually floating the dispenser at a set height above the substrate so the ink can be pressed into the substrate. This set height needs to follow the surface of our substrate, so we use the probe to measure across our substrate to generate a heightmap for the dispenser to follow.
In the target quality step, we’re telling NOVA what to expect with our materials. Each entry here will affect the print settings for our new material. For example, if we decide to use a different nozzle diameter, we’ll need to run the procedure again to ensure the settings are properly adjusted. The parameters we can set are as follows:
Nozzle Diameter: This should be set to match the inner diameter of the nozzle being used
Trace width: This tells the software what width we expect the trace to be once printed with our set nozzle above. The software uses this information to determine how close passes should be when drawing an object, so there is enough overlap to fill an object nicely.
Print Height: This sets the standoff distance from the top of our substrate to the tip of the nozzle. The dispenser will maintain this distance when dispensing across our substrate.
Temperature: This sets the temperature the dispenser will heat up to for printing. This allows us to eliminate the fluctuating temperatures day to day as a factor in our print settings. For inks that are more temperature sensitive, this can be set to room temperature.
Print Speed: This will set the motion of our tools in XY when dispensing. This can have an effect on how much material is dispensed at a given location while in motion. For example, the same print pressure done at half the speed will dispense twice as much ink.
For our print we will use the following settings:
Nozzle Diameter:
150 µm
Trace width:
180 µm
Print Height:
60 µm
Temperature:
35°C
Print Speed:
400 mm/min
We've already done this so we can now mount the dispenser and click next.
This step gives us a starting point to begin testing our ink. There is no exact pressure we’re looking for here, we just want to ensure ink is at our nozzle and starting to flow a bit. To do this, the dispenser will move to hover over the drip tray and slowly increase the dispense pressure until we tell it to stop. We’re looking to see about 1-2 mm of ink flowing out before we hit the Stop button (or space bar).
We’re finally ready to start calibrating our paste. The software will guide us through 3 steps to repeat until we have settings we’re happy with.
Looking at the picture, the software asks us to rate our pattern based on a few criteria. The primary focus on our first few prints is Width and Leakage:
Width (Pressure): Are we putting down enough material or too much, is our trace width too thin or too wide?
Leakage: Is there ink leaking out of the nozzle in between features or are there big gaps at the start of features? Another way to check on leakage is watching the piston movement in the ink cartridge. If the piston is moving excessively then we need to increase the leakage.
Later on we can click on Advanced to tune the starts and ends of our traces as well.
Now that we have our material settings calibrated and they are accessible in our materials library at anytime, we can move onto the next print exercise.
We already did this step in preparation for the exercise, but if you missed it you can go back .
