Week 4 assignment: Electronics Production
Summary
This week's goal is to characterize the design rules for the in-house PCB production process and document the workflow for sending a PCB to a board house. Also, I had to make and test a microcontroller development board.
Having done quite a few tests, it was possible to find the production parameters, however, I found it a little difficult and with many things to consider that are detailed below.
Process
The Fablab has a Roland machine model: MDX-540 in which the PCB traces and outline cut were made.
The process to begin manufacturing a PCB is detailed below:
1) We start with an image in PNG format with the traces to be made for our PCB. This information is processed on the FabAcademy web simulator: "https://modsproject.org/" to obtain the G code as a result.
Important Note: It is important to work with a high quality image.
It is also possible to work with a file in "svg" format, depending on the software with which the circuit design is being worked on.
2) Now in the web simulator, we proceed to configure the parameters we want. After several testing in a fiberglass board, we define the following parameters:
- Work with a cutter diameter of 0.1mm and a cutting depth of 0.1mm.
- 4 offsets and a stepover of 0.5.
- For the traces the 0.30mm mill was used and for the outline the 0.8mm.
3) With the configurations already set, we proceed to calculate the G code and we can see how our work would turn out. G codes are used to command specific actions for the machine: such as simple machine movements or drilling functions.
4) Once calculated, the G code file is automatically saved to the computer. Finally, this file will provide all the instructions and coordinates that the Roland machine needs to be able to manufacture the PCB.
Important note: It is necessary to correctly calibrate the 3 axes. The "x" and "y" axis will help us position ourselves on the lower left side of our board, using the "origin" command. For the "z" axis, it is necessary to calibrate it every time the milling cutter is changed with the "z zero" command.
If there is any error in the calibration of this axis, the machine head will begin to move without any direction as can be seen in the following video. In this case, it must be reconfigured by adjusting the position of the cutter with respect to the jaws.
PCB manufacturing
The PCB manufacturing process began with the "svg" file loaded into the simulator "https://modsproject.org/" configuring several of the parameters. Each of them yielded a different quality on the board as shown below:
First test parameters: - "svg" file
- tip diameter: 0.1
- angle: 30 degrees
- Offset number: 2
- cut depth: 0.15
Second test parameters: - "svg" file
- tip diameter: 0.1
- angle: 30 degrees
- Offset number: 4
- cut depth: 0.10
Third test parameters: - "svg" file
- tip diameter: 0.1
- angle: 30 degrees
- Offset number: 4
- cut depth: 0.09
Recommendations to take into account:
-cutting mill in good condition
-fix the entire board with double contact tape
-use lubricating oil when milling
-remove dust with a vacuum cleaner
Finally, we test the copper tracks and confirm that there is continuity of current between them, ensuring optimal manufacturing quality.
PCB solding
The board soldering process begins after the manufacturing of the copper tracks is completed. At this stage, the following components are soldered:
-3 LEDs (test diodes with multimeter)
- 1 SMD female pin header (x6)
- 1 pin header SMD male 90 degrees (x10)
- 1 SMD push button
- 4 1k resistors (1001)
- 1 470k resistor (4701)
- 1 seeduin
After the board was solded, I wrote a simple code to turn on the 3 leds at the same time at the moment the button is pushed.
Files:
Programming code