4. Electronics production¶
Assignment
- Characterize the specifications of your PCB production process (group assignment)
- Make an in-circuit programmer by milling the PCB (program it, so that you can use it to program your board in Electronics Design week, and in other weeks)
- Optionally, trying other processes.
Topics
- How to use Mods system
- How to use Roland RSM-20
- Soldering PCB
- FTDI design inspired from Leon Fablab Adrianino.
1 Fabricating PCB¶
Antti Mäntyniemi Fablab Oulu Manager and Fab Academy 2016 alumni, gave us the local lecture about Printed Circuit Board (PCB) fabrication. In my fablab experiences, this was the first time using CNC machine. PCB’s electronics pattern creation technique has 2 methods, chemical etching or physical machining. This time is made by CNC machining, we have Roland SRM-20 in Fab Lab Oulu.
We are going to make the Arduino based computing board following this Fablab Leon’s Adrianino and this time as PCB exercise, we focus on making a USB-UART-interface or as a UPDI programmer.
1.1 Mods system, converting files¶
The PCB image of UDPI programmer is download from here.
First open Mods system by browser. By right clicking, programs -> Open server program -> Roland SRM-20 PCB svg.
Then load the file of SVG file, then set “Invert” and dpi to 2400 (can be modified later with production quality)
This PCB pattern is for mill traces, select that and then put the value of tool diameter. The diameter is all up to the design, check by calculate and select proper value. Be careful for missing layout, pad, line,,,, (later you will cry by this failure…)
After click the calculate, you can check the SVG design by clicking View button of SVG image box below.
Setting by 0.25mm diameter. Some missing design there.
Setting by 0.22mm diameter, as drawing this is OK.
For Roland SRM-20 milling machine setting, put all origin to 0mm. And then change the file output from Websocket to “File Save”. First delete the Websocket component then with right click,
Modules -> Open server module -> file Save
then left click for each “file” object makes the connection line.
Got the trace data for milling PCB.
And PCB outline for cutting out, load the file of interior -> invert -> select outline -> calculate, the same procedure except selecting outline than trace.
1.2 Milling machine¶
Let’s mill and cut the PCB, using Roland SRM-20.
For the preparation of PCB, this time we used FR1 PCB raw board. This FR1 is softer than FR4 and cheap (,,,but can be burned, not robust. But prototyping and hobby use are well enough).
To set the FR1 PCB board into milling machine, the board has to be fixed firmly and flat straight enough to set into the machine. Check the straightness of the board, can be fixed by bending. Use the double side tape to attach the MDF board on the machine. This is 0.01mm world,,, very small bending of the board can effect the quality of milling.
There are 2 different milling bits, one is for tracing V shaped 0.2-0.5mm bit (orange) and another one for cutting bit (white)
For tracing mill, I put the V shape bit and set the XY origin first.
I opened VPanel for Roland SRM-20 in the PC connected to milling machine using hex key.
I moved the bit to the corner of PCB raw board by clicked X/Y button by the cursor step of x100. (cannot put the number of position directly…)
Then the bit was moved to proper corner point, I set the XY origin by pressing X/Y origin button of right upper side of VPanel.
After set the X/Y then need to locate the origin Z. First, put the bit down lowest enough by pressing the button of Z (-Z, lower one) by the step of x10 carefully, if the bit hits to the board, the bit is easily broken. Just before 1mm or more, stop and loose the bit, manually I put on the surface of the PCB board. And again, don’t drop the bit, easily broken.... Then tight the bit on that Z position.
After made the Z position of bit on the PCB surface, press the origin Z in the set Origin point of VPanel right upper side.
I pressed “CUT” button in VPanel, and deleted all the previous cutting files. I clicked “Add” and selected the trace file .rml format. I pressed “output” and tracing started. Milling starts!
To check the production quality, I stopped on the beginning part of cutting and checked the board. Pressed “Pause” button to stop operation, and pressed “View” button in move in VPanel. Opened the door and vacuum the dust then checked the quality. After checked, I resumed by clicked “Resume” and the operation is automatically resumed.
Yes, my first milling product!
1.3 Soldering the components¶
Soldering the components on PCB, there are good work station in Fablab Oulu at the room of Protopaja.
- Vacuum air exhaust facility, keep your health from the toxic smokes by soldering.
- Micro scope can help the handling of soldering iron especially for very small components of surface mount.
2. FTDI/UPDI board¶
FTDI is from the company name, Future Technology Devices International Limited is a Scottish privately held semiconductor device company, specializing in Universal Serial Bus (USB) technology.
This time, (FT230X)(https://ftdichip.com/products/ft230xq/) is used for PCB fabrication exercise, this outcome is useful for later electronics exercises.
This board has two functions,
- FTDI serial connection using in serial monitor, jumper pin is put on upper side.
- UPDI programming when upload the code to IC, jumper pin is put on lower side.
Test the FTDI serial interface by loop back from output(Tx) to input(Rx).
Checked by Putty, enter the letters by keyboard then the signals are returned to the serial monitor as shown letters.
2. Group assignment: Characterizing milling machine¶
Group work is done with Antti and Mona by cutting two boards with different milling bits. The report is shown in this link.
Reflections¶
- Check carefully the image that came out from Mods.
- PCB milling quality is very sensitive by the flatness of PCB board mounting.
- The size of milling drill makes variation of the speed of process but also the resolution of outcome quality.
- Soldering to PCB with surface mounted components are needed really careful handling with delicate movement of the iron. It is much better to use the microscope to check the quality and makes much easier.
Used files¶
FTDI-UART-UPDI svg, rml files
Group work, Line test files