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Week 4: Electronics Production

  • Characterize the design rules for your in-house PCB production process: document feeds, speeds, plunge rate, depth of cut (traces and outline) and tooling.
  • Document the workflow for sending a PCB to a board house
  • Document your work to the group work page and reflect on your individual page what you learned

Our workflow for the SRM20

Mods Importing files on SRM Tools used and for what... Using the mill

Creating the milling job (PNG)

  1. Open modsproject.org

  2. Right click > 'programs' > 'open program' > 'Roland' > 'SRM-20 Mill' > 'mill 2D PCB'

  3. Add the linetest_traces.png files (ensuring traces are white)

  4. Click 'mill traces' (1/64)

Mods with the traces file loaded
  1. Ensure the 'save file' switch is toggled
the mill path has been generated

  1. Click Calculate

  2. A .rml file should be downloaded, rename this to traces.rml

  3. Repeat this process for the edge cut (Use mill outline instead (1/32))

  4. Rename the outline file as outline.rml

Using the mill

  1. Cover the back side (non copper coated) side of the PCB blank
Adding tape to the backside of the PCB blank
  1. Stick this to the block on the SRM-20
blank mounted to the mill

  1. Turn on the machine

  2. Connect via USB with the Roland Vpanel application

  3. Insert and tighten the bit in the chuck, load the 1/64 first (Use the 1/64 for traces, 1/32 for holes and edge cuts)

Both of the milling bits
  1. Set the zero point of the machine, get the milling bit to touch the front left corner(of where the PCB ought to be milled) of the PCB blank, use the Vpanel application to move the bit around the workspace
the mill bit to the bottom left corner
  1. Load the traces file, click 'cut' to start the job
milling the line test traces file

  1. Once complete, move the gantry upwards, load the 1/32 milling bit, move the gantry back set the 'Z' zero point only

  2. Load the outline file and cut

Characterise the design rules

Our first run didnt acheive a full depth cut, this was because the block was low on that corner, we moved towards the center and increased the depth of cut for the second attempt and was successful.

the first go at the line-test

Upon doing some destructive testing (trying to peel up the traces), we were able to dial in our minimum track width to 0.4mm (15.7 mil) and 0.5mm track clearance (19.7 mil).

All of the speeds and feeds were left as the default in Mods. Increasing the depth of cut to 1.2mm was needed if using the bottom left side of the block.

the second go at the line-test, traces had seperated

Document sending a board to a Fab House

Later on Liam sent a board off to PCBgogo.

After generating gerbers for the PCB its as easy as zipping them and adding to the instant quote page.

We changed the surface finish to 'HASL lead free'. Paid and sent them off.

Once they arrived they were really good quality.