Skip to content

8. Electronics production

PCB_1

Overview of week 8 assignment

  1. Group assignment
    1. characterize the design rules for your in-house PCB production process
    2. submit a PCB design to a board house
  2. Individual assignment
    1. make and test a microcontroller development board that you designed
    2. extra credit: make it with another process

1. Group assignment

For more information, see the Week 08: Group assignment page.

2. Individual assignment

I made the microcontroller development board I designed in week 6, Electronics design with Fusion Electronics.

A. Data for PCB milling

Because of the CNC milling process, each file needs to be separated depending on the type of work.

  1. Traces: Mill only copper surface to isolate traces
  2. Logos (Optional): Clear copper inside
  3. Holes: Holes through to the bottom of circuit board (be careful which side to cut)
  4. Outline: Cut out the PCB outline at last

PNGfiles

In the next step I used mods to create G-code for CNC, milling the black side of the border between the white and black of PNG files. So, I prepared PNG files suits the step (Logo and Holes need to be inverted in the "mods" step).

a. Export PNG from Fusion Electronics

  1. Prepare "Outline"
    1. Draw a rectangle slightly larger than board outline (yellow lines)
    2. Select BoardCutline (yellow lines only)
    3. “Convert To Polygon” to copy it to another layer (the polygon filled in white is for export)
    4. Export the polygon as PNG (this is not the rectangle shape but your board shape) layers

  2. Prepare "Holes"

    Fusion Electronics requires special steps to drill the through holes (Note: Add a hole).

    How to create drill legend for manufacturing PCB in Fusion Electronics

    1. Measure diameter of the holes
    2. Change grid size: VIEW > Grid > 0.5mm
    3. DESIGN > PLACE > Hole (NPTH) millholes
    4. AUTOMATE > Run ULP > Browse “drill-aid” > Drill center diameter > “0”
    5. Change layer “116” color: Details > Appearance (black > white)
    6. Display only layer "116" drill_aid

  3. Export each layer (traces, logo, holes and outline) PNG

    1. Show the trace layer and hide the others (by unselect "Component" at the Selection Filter at the right to hide + marks of components)
    2. DOCUMENT > OUTPUTS > Export
      • Check "Monochrome"
      • Resolution: 800dpi export

b. Generating G-code using mods

  1. Go to mods
  2. Right click on the white canvas
    • Program > Open program > machines > G-code > mill 2D PCB mods
  3. Select PNG file on the left
    • Select default presets: set PCB defaults
    • To only isolate trace: isolate traces (1/64)
    • To mill outline and holes: mill outline (1/32)
    • Invert PNG if needed because the black side of the border between the white and black of PNG will be milled (in this case, holes and logo are need to be inverted) mods_settings
  4. Generate toolpath at the middle: mill raster 2D
    • Change tool diameter if it needed (For holes and outline, we changed tool diameter to “0.7mm” since the endmill we used was 0.7mm diameter)
    • Generate toolpath: calculate
    • Preview: view (3D preview didn’t work without reloading the Mods) mods_preview

B. PCB milling

a. Milling

A detailed workflow for PCB Milling can be found on the Group assignment page.

PCB_milling

I forgot to mill the hole and was about to remove the PCB after milling the outline, but luckily the double-sided tape was strong enough so I was able to drill the hole at the end.

b. Sanding

I underestimated the wear on the end mill and the end mill I used was not new, so there were quite a few burrs, but after sharpening it was fine. I also removed some small chips between the traces to avoid potential shorts.

sanding_PCB

C. Soldering

a. Stuffing

I organized the components on the milled PCB and checked where to solder and direction of each components such as LED and tact switch.

stuffing_soldering

b. Dirty soldering

I was new to soldering especially surface mount one, so I watched videos to learn the basics and started with pin sockets. I struggled at first. While soldering a resistor, I accidentally burned the pin header.

dirty_soldering

D. Testing

  1. Functionality
    I tested the board with Arduino code by turning on the LED and pressing the switch.
    • The switch worked, printing to serial as expected
    • The LED didn’t turn on

  2. Troubleshooting (on the next week)
    I was able to check the direction of the LED using a button battery, and simply it was the wrong orientation. With help of our instructor, I could fix it by following steps:

    • Remove the LED (hold the LED with tweezers, heat the solder, and the board will fall off)
    • Apply flux, and remove remaining solder using solder wicking wire
    • Solder the LED again and checked.

    LED_resoldering

3. Files

Afterthoughts

  • CNC milling is fun.
  • Soldering is not fun so far, but it takes practice.
  • At first the soldering was messy and embarrassing, but from a distance it's not so obvious.