8. Electronics Production

Group assignment:

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

Roland SRM-20

We usually used two types of endmill. We use the 1/64” end mill for cutting out the traces. The 1/32” end mill is used for cutting out the borders.

Preparing the Copper Board for Milling

Our lab has been using these sacrificial underlay over3 years. We decided to changed the underlay.

We removed the old underlay. Cleaned the underlay bed.

We start by preparing the copper board for milling. We collect all the required materials.

Place you copper board on the sticky side of the tape and make sure it is flat witout wrinkes in the middle.

The placed the pcb on the SRM bed and press gently.

MODS for SRM-20

Make sure you are using the correct port. Press the button to turn the machine ON

First, download the two linetest image files. These files help test the accuracy of your bits and machine by milling thin lines (0.001” to 0.02”), which is useful for determining the trace width of your circuit.

When you land on Mods page right click on red and blue icon, Click on Program.

Click on open program

Click on SRM 2D mill

You can either select the PNG file or the SVG file for the as SRM 20 support both the file formats >select 1/64 for milling the traces > Click calaculate and this generates a path for the milling.

This might take times as per you design. After generating the path, turn on the 4 and click on calculate to download your files.

Next we select 1/32 for milling the boarders > Click calaculate and this generates a path for the milling.

We followed the same procedure as above to download the rlm files

!!! note Setting for the 1/64 endmill - Cut depth -0.004 in
- Offsetnumber-4
- Offsetstepover-0.5
- Cut speed- 4mm/s - direction-climb

!!! note Setting for the 1/32 endmill - Cut depth -0.024 in
- Offsetnumber-1
- Cut speed- 4mm/s - direction-climb

Note

1/64 endmill - 8000-9000RPM
1/32 endmill - 8000-9000RPM

Milling

Use the allenkey to loosen and tigthen the screw

Open the VPanel for the SRM-20 and use the keys to move the spindle to your desired location. Always choose the optimal position to avoid wasting the board.

First, move the spindle to the corner of the board using the X and Y keys.

Then, set it as the home position by clicking X/Y under Set Origin Point, shown in the image below.

Secondly, Move the spindle to the center of your milling area, then slowly lower it using the Z key on the VPanel.

Note

Switch the cursor step to x100 or x10 to lower the spindle slowly and avoid hitting the board, which could break the end mill.

Once okay with the z setting, click as shown in the image.

Roland SRM-20 is ready to mill your board.

Select the .rml files downloaded from MODS by choosing Cut > Add (ensure all other files are deleted), then open the file and click Output.

Line test result

Result

We successfully fabricated a test board using a 1/64" milling bit, which achieved a precise 0.001" trace width. However, the trace was too narrow for clear visibility. As the milling width increased, the traces became more distinct.

The 1/32 endmill was perfectly able to cut the edges.

This test board serves as a valuable reference for selecting optimal trace dimensions in future circuit board designs.

Pcb engraving using our Mr Carve

Mr Carve has four different laser sources

Fiber laser
Co2 Laser
YAG laser
UV laser

We set the different setting for the different laser source Fistly we choose the fiber laser source and used the following parameters

Next we tired using the UV

Then we tired for the Co2, used the following the setting for the parameters

Lastly we tired using the YAG

Following are the result of the each laser source. For fiber laser source the egnraving was not that good as it engraving everything.

So our group decided to use Co2 laser source for engraving, we increase the duration of the engraving using the co2 laser. We engrave it more 45mins, however the result was not as expected. So our group decided to explore this in future.

Reflow Process

This week we also tired using the reflow method. This process melts the solder, which sticks the parts to the board, and then cools it down to make strong, secure connections.

Reflow workflow

Apply Solder Paste: A special sticky paste (solder paste) is spread on the PCB pads using a stencil.
Place Components: Tiny parts (like resistors, chips, etc.) are carefully placed on the board where the paste is applied.
Heat the Board: The board moves through a machine with different temperature zones:
Preheat: Warms up the board gently.
Reflow: Heats it up more to melt the solder paste.
Cool Down: Lets the solder cool and harden.
Inspect the Board: After soldering, check the board to make sure everything is connected properly.
Clean the Board: Remove any leftover sticky stuff (flux) or extra solder to keep the board clean.