PCB Fabrication

diy professional double sided pcb

by:A-TECH      2020-01-18
Today, very cheap PCBs are available from China.
But let\'s say that you need to have one in 24 hours, then the only option you have is to do it yourself.
Also, it\'s way more challenging and fun!
In this note I will guide you through the whole process of making a professional double
Double sided PCB on cheap CNC factory without any chemicals!
Features of PCB: I spent a lot of experiments to achieve this.
In particular, some work needs to be done to simplify the process for soldermask and screen printing.
Let\'s start!
Cheap CNC tools are perfectly qualified for the job.
About 150 units in China-300$.
Parts can find cheap parts on AliExpress or ebay with the names of these parts written on them.
Chemical tin solutions can be difficult to find and can be expensive (
About $50 a bottle)
But completely optional.
The PCB stand and the alignment pin stand are used to mount the PCB on the CNC bed.
You can print them from a zip file or from the original designer, and 2 copies are required for each file.
In addition to the CNC factory and a few tools, we also need 3 programs to make our own PCB design software for the iMac, you can use any PCB design software you want.
Popular options include: Altium designer, Circuitmaker, Eagle, Kicad. . .
I assume you know how to design the pcb and export the gerber file.
If you don\'t know what these are, creating a gerber file for a PCB is like generating a PDF for a text file.
This is the standard format for saving PCB specifications.
You can find a lot of tutorials on this online.
FlatcamFlatcam is not common but is easy to use.
I will explain each step in detail and guide you all the way.
Check out the excellent Flatcam manual when in doubt.
Flatcam will convert our gerber file into machine motion (gcode)
Through a technology called isolated routing
To grind the PCB track, we have to grind the outline of the track to isolate it from the copper around it, hence its name.
There are 4 labels in Flatcam (see picture)
: We first Open a gerber file with file> Open Gerber, which will appear under the projects tab.
Now there are 3 steps to convert this gerber into gcode: for each layer of the PCB, this simple process must be repeated.
The specific settings will be described in the next steps and mentioned in units of measure.
The feeding speed will depend on your actual machine.
Reference: my CNC has a 300W spindle.
Control of CNC machine tools with Candel del;
Another popular option is pepper.
Any software works as long as it has the option to make a height map (
More information later).
If you have a CNC machine, you will be familiar with most of the options and how to control the machine.
I will detail the PCB specific options we need.
Let\'s start milling!
Before we start milling any side on either side, we have to make sure that we are able to flip it once the top is milled.
To do this, we will create alignment holes so that we do not lose positioning when flipping the board.
You can skip this step if you only need a single sided PCB.
Flatcam set upwe must use double
The two-sided PCB tool for Flatcam can produce alignment holes.
I prefer to drill 2 holes, each at the far end of the PCB, about 5mm from the edge.
Because my pcb is 150mm long, I put them at coordinates (5,0)and (145,0).
The diameter of the hole is 3mm.
This creates a gerber file with two aligned holes.
Now, we can convert it to gcode as per the procedure I described in the previous step!
Select the file and go to the selected tab: Finally, export the result file.
It\'s time to put the gcode into the candle and grind the alignment holes.
First, put the PCB into the PCB Holder installed on the CNC bed.
Two alignment pin brackets were also added, but they were temporarily placed on the side of the PCB.
Open the gcode file and install the 3mm mill in the CNC.
Next, center the Origin vertically and 5mm from the left edge of the PCB (see picture).
Start the program grinding the alignment hole.
As shown in the figure, two 3mm alignment pins are placed in the holes we drill and through the alignment pin bracket.
The PCB is now firmly installed and can be flipped in the future!
From now on, don\'t change the location of your home!
We can start creating the actual PCB now.
Before milling any traces, we will draw the outline of the board and create a height map of the PCB.
Outsource the board to your board profile gerber File for milling into Flatcam and go to the selected tab as usual.
Under plate cut, enter the settings mentioned below.
We will do this in 8 shallow channels.
After generating gcode, install a 2mm milling bit in CNC and start the program!
The PCB will be fixed in place by 4 tabs and very sturdy for upcoming operations.
When milling a PCB, creating a height chart is one of the key steps to achieve good results.
In order to get a good PCB, the cutting depth of the entire PCB should be completely uniform.
The copper sheet is never completely flat, so it is ground too deep in some places and not deep enough in other places.
We can avoid this by detecting the PCB height of several points and adjusting the mill depth accordingly, so that the cutting depth is the same anywhere.
We created this height map with the Z probe: by connecting the crocodile clip to the milling bit, connecting the clip to the PCB, the CNC can detect when the two come in contact (
Because they finished a circuit).
This feature is implemented in candles: we are now ready to grind the actual traces, let\'s go!
The top layer can now be ground.
We will do this in 4 steps: first grind the copper trace, then apply the welding cover and solidify, then grind the pad and finally add the screen printing.
First of all, we grind the copper layer with isolated wiring.
Using the settings below, the gcode file is generated the same as before.
Set zero Z height with your Z-
When milling, be sure to use the height chart to get good results.
Once the copper is ground, we apply a UV curing welding mask.
Disperse it on the PCB with a uniform scraper, but do not apply too much pressure.
In addition, leave the PCB in place, otherwise the height map will be useless!
This is the key to the next step!
Once applied, weld the mask with UV curing until it becomes hard.
The grinding pads now cover the entire PCB on the solder mask, so we have to release the pads again.
We can do this with zero milling depth.
This is where heightmap shows its strength: it allows the solder mask to be worn out, but the underlying copper can be left tactfully!
Since we need to grind the interior of the pad, not the profile, we enter the negative tool diameter.
Make the screen printing finish the front and make it look like a proper PCB, one more thing we need: screen printing.
In a professional process, the text is printed on the top of the welding mask, but this is difficult to reproduce.
The trick I found was to grind the text in the welding mask like in the previous step, instead of printing it on the top.
Then apply the correction liquid and polish the top, and the screen printing is embedded in the welding mask!
The front is done and we can move to the back.
When the PCB is completely cut out, I leave the sanding to the end.
Bottom milling is-ofcourse -
Very similar to the top.
However, there is an additional step: we need to flip the PCB and mirror the gerber file before generating the gcode.
First mirror gerbersFirst, load the gerber file for the bottom.
In order to mirror the gerbers, we have to use the double
Use the double sided PCB tool again.
Select the layer through the drop-down menu and press the Mirror object.
Do this for the following layers: the process of generating gcode is now the same as at the top.
Flipping the board is as simple as it sounds: loosen the PCB fixture, but keep the alignment pin unchanged.
Flip the board and re-
Fix it in the clip.
Now you can create a new height map as before.
The last step on the mill is drilling.
We will drill holes in two sizes: 1mm and 1.
Plated 5mm-holes.
This is one of the main advantages of grinding compared to etching pcb, because etching requires manual drilling.
Expand to open the drilling file, select open excel on instead of open Gerber and select the correct diameter in the selected tab.
The other steps are the same.
This is the last step and we can now remove the PCB from the CNC.
And cut off the label that keeps it.
Our beautiful screen printing shows the light polished with fine mesh sandpaper. Still, vias
The complete steps for hole installation of our PCB are mounting holes and through holeshole plating.
You can buy these cheap vias online in different sizes.
For vias, use 0.
The size of 9mm and insert it into the hole of 1mm.
Use the DingTalk driver to turn off the other side of the hammer and establish a strong connection between the top and bottom.
Plated-Hole use 1.
The 3mm variant is in 1. 5 mm hole.
Since the holes need to be kept open, curl these holes with tools as shown in the figure.
As an optional last step, the PCB can be colored.
This makes it easier to weld components to the pads and prevent them from corrosion.
We do this with a solution called liquid/chemical tin, which is basically dissolved tin that can be combined with any copper it touches.
However, wear gloves when dealing with these things!
Just pour the liquid tin/chemical tin solution into a container large enough and flood the PCB.
Let it sit for about 2 minutes and take out the board (wear gloves! ).
Rinse under water and you will see shiny tin pads and perforated plating!
We have a pair now.
Double sided PCB with welding mask, through hole
Hole plating and screen printing ready for assembly.
If you want to know what we have milled, this is an LED bar driver based on IR.
Finally, let\'s talk about the elephant in the room: how about etching the PCB?
I \'ve tried etching before and personally I don\'t really like to use and store chemicals.
On the other hand, you don\'t need a CNC factory, which can be an obstacle for some people.
A significant advantage of milling is that the cut and drill holes are not manually processed and therefore have better alignment.
In terms of time, I have tried two methods, and the time spent is more or less equal.
On the one hand, you have to generate gcode when etching requires toner transfer (or similar)of the gerber.
It takes time for milling and time for etching.
While etching is faster for larger printing, you don\'t have to stand next to CNC either.
Finally, it all comes down to personal preferences;
Make the pcb the way you want to make you feel comfortable! :)
Conclusion when you are in urgent need of professional double sided PCB, you still need to make it yourself.
With this Instructure and CNC mill, you should be able to do this now!
It is not intended to compete with commercial pcb, but it can save you costs if waiting for manufacturing and shipping is not an option.
Also, I really enjoyed the challenge of producing my own pcb with CNC factory including screen printing.
Hope I gave you some inspiration to try it yourself!
If so, please vote for me in the PCB contest.
Hope you enjoyed the project!
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