5. Electronics production

Traces png and settings in fabmodules

• In menu on top
• Input format: image (.png) ; and choose the png file for your outline
• Output format: Roland mill (.rml)
• Process: outline 1/32


• In menu on right
• machine: SRM-20
• offset (x0, y0, z0): 0
• tool diameter (mm): 1
• Press calculate
• Once done, press save to download the file

Outline png and settings in fabmodules

• The size from both files (top right corner) is equal
• The size is what is expected

Mill the board

1. The tasks to PREPARE THE MILLING MACHINE are:


1. Open Vpanel application in the assignated computer
2. Switch on machine
3. Open machine and extract the bottom plate
4. Check sacrifial board is leveled (not done by us)
5. Stick the board to the sacrificial board with doubled sided tape
6. Back in place and hold well

1. vpanel view

2. switch on the machine

5. Prepare the board to be stuck to the sacrificial board

6. Screws that hold the plate on the base of the machine
2. Prepare the TOOLS



1. V Shape bit for milling

2. Bit for cutting

3. Hexagonal allen

4. Spatula
1. V Shape bit.
   • this is the bit we will use for milling the traces
   • It's diameter goes from 0,2mm to 0,5mm, being the part we work with of around 0,4mm
2. Bit for cutting.
   • this is the bit we will use for cutting the outline of the board
   • it has a diameter of 1mm
3. Hexagonal allen
   • We use this allen to screw / unscrew the bit from the head
4. Spatula
   • We will use the spatula to extract the board, once finished, from the big piece of board
3. SET THE ORIGO
We need to first understand the front panel of the application V-Panel for SRM-20.

VPanel Front panel description
We will be first doing the traces and then, cutting. So the process would be:
• Put the bit for the traces
• Set the origo
• Trace, using the traces file
• Put the bit for the outline
• Set the origo
• Cut, using the outline file
The steps to set the origo for one bit are:
1. If you need to change the bit then:
• With the lid closed, press View on the Vpanel to put the head close to the front part
• Open the lid, and unscreew the bit enough you can remove it from the head. It is better to hold it with a couple of fingers.
• Put the new bit and screw it in
2. Setting X, Y
   • If you are changing from milling bit to cutting bit, you should not change the XY, or you would not cut on the expected place
     • You can put it back to the XY origo if necessary by pressing the button indicated in the picture above
   • If you need to set the X, Y
     • Press the XY cursors to move the header to the desired X,Y position. This can be done with speed > continuous
     • When the header is in the correct X,Y position, set the X,Y origo by pressing the corresponding button in the panel
3. Setting Z
   • Press the Z cursor to lower it as much as possible without touching the surface. In this case use speed > x100 and reduce it to speed > x10 or even speed > x1 if needed. It is important not to touch the surface, because the bit could break.
   • Open the lid, hold the bit with one hand while unscrewing the bit slightly. Help the bit to fell until it touches the surface.
   • Holding it still, tighten again the bit to the head.
   • Close the lid, and set the Z origo by pressing the corresponding button.
   • Move the head up a bit with the Z cursor
     • This is because Jari had once a bad experience with the head not doing that when preparing to cut
Now, the origo is set. Finally we can choose the file. Press Cut in the vPanel, and a new menu is prompted:
• Press Delete All to remove all files in the list
• Choose the file (First, the traces; Secondly, the outline)
• Press Output

Origo for bit for tracing

Tracing

Waiting

Origo for bit for outlining

Outlining

Result

Vacuum clean the result

Extract with an spatula

Result

There are still a couple of things to do:

• Remove extra copper. As this is meant to connect to the computers' USB port, it is better to remove the extra copper from the tip

Use a knife or cutter to remove extra copper

Result.
• Scrub upper coatingThe boards used are FR1. They have an extra coating that needs to be rubbed away because it makes soldering quite challenging

Before scrubbing

Scrubbing

Final result.
It can be easily appreciated in the last picture the difference of colour between the original board and the brushed one.

• The board is not traced correctly, with some parts traced or semitraced and others where the copper remains almost completely in the traces. This is most probably due to having the sacrificial board uneven, so the actual board does not have the same Z position in all its surface
  Example of not leveled sacrificial board
• If you do not see enough "dust" coming from the bit, then most probably it is not milling. Or something is wrong (for example, the bit is not screwed tight enough), or the cut depth is not enough.

Soldering

I checked from Brian's page the list of components needed:

• 1x ATtiny45 or ATtiny85
• 2x 1kΩ resistors
• 2x 499Ω resistors
• 2x 49Ω resistors
• 2x 3.3v zener diodes
• 1x red LED
• 1x green LED
• 1x 100nF capacitor
• 1x 2x3 pin header

I then used Iván's way of organizing the components, by sticking them to a tape, close to their description.

Components needed with their corresponding description..

To Know where to solder the different parts on the PCB, we had to use the schematic and board shown bellow (from Brian's page )

Board image showing components exact placement

Schematic showing components placement and value

Taking into account the information in the last images, I completed the list with the components' names given in those images:

Components needed with their corresponding description and placement

Then, I prepared the soldering place:

Switch on the ventilation

Soldering station, lead-free solder, desoldering braid

The plan for the board was:

• start with the chip (just because I thought it was harder)
• then, go from right to left soldering

Switch on the soldering station, and wet a bit the sponge on the base.

Then, I followed these steps to solder one component are:

• put a bit of solder in the pad of one of the sides/legs to hold the component
• position the component over it and heat the solder with the iron tip so it melts enough to hold the component
• proceed to solder the other side/legs of the component
  • if the component has several legs, you may start from one corner, and then continue with the opposite corner; and then with a leg on the other side. This way, the heat is better dissipated.
• Soldering properly the first side/leg, that is, resolder the first pad that was holding the component

Bit of solder

One leg

Two legs.

I decided to start with the chip, because I thought it would be the most difficult (and if I really messed it up, I could go back to the milling process fast). Then, I continued soldering the rest of the components.

All the components placed!!

Things that can go wrong

• There are some components that require certain orientation in the circuit. That is the case of the LEDs and the Zener. Check the marks!!
• shortcircuits, that is, solder that joins two different paths: use the desoldering braid to remove the solder
• components bad positioned: use the desoldering braid to remove the solder

How to use the desoldering braid

• Put the thread over the solder to remove
• Press with the soldering tip until the heat melts the solder
• Pull the tape fast, and the solder gets stuck to it