Fab Academy 2013

FAB LAB UNI | Lima - Perú

Electronics Production

Milling the circuit board and welding the Fab ISP


Materials & Equipments

  • CNC Mill: Roland Modela MDX-20
  • CNC Laser Cutter: Epilog Legend 36EXT (if you cut the board milling you need a 1/32" end mill)
  • 1/64" (0.4) End Mill Bits
  • Single layer coper plate board
  • Dual side adhesive tape
  • Fine Sand Paper (NÂș800 or high)
  • Electronic Components (left for the Xtal Circuit, right for the resonator circuit):

  • Welder w/ SMD welding tip
  • Welding Flux
  • Solder wire
  • AVRISP2 Programer
  • USB to micro USB cable

  • Before Milling Process

    In order to generate a circuit path for the Roland Modela, we used the Fab Modules in Ubuntu OS.

    Editing the Fab ISP source image

    The board model was download from the electronic production page at the bottom.

    I like to personalice my circuit, so that, I put my signature logo on the free space of the boards

    I fabricate the two boards (with resonator model and without one). For mill it I placed both boards in a same image file.

    Loading the Fab Modules

    Then load the Fab Modules. Open terminal and type in "sudo bash":

    [email protected]:~$ sudo bash 
    [sudo] password for fablab:

    Write the password of sudo mode, then type in "fab":

    [email protected]:~# fab

    The Fab Tools window will appear. Pic [Image(.png)] in format popup and [Roland Modela(.rml)] in process popup, and click

    Another window will appear with three columns:

  • The first left is for loading the image file with button. If you do some modifications to the original file (like me) check the circuit dimention and resize if is necesary with .
  • The center column is for the path generation and view .The parameters involved are:
  • - [diameter(mm)] is the diameter of the mill sharp point
    - [offsets(-1 to fill)] controls the thickness of the gap between the path and de useless copper zones, if you want leave only the paths and clean all the other zones use -1.
    - [overlap (0-1)] is the fraction of area that the mill pass over the uncut region
    - [2D threshold(0-1)] is to control the border recognition.
    - [2Dz(mm)] is the cut depth, for our boards and mills we used 0.08mm of depth;

  • The right column is to create the Roland Modela file and to the machine:
  • - [speed(mm/s)] is the speed of cutting movements. The value depends from the cutting material, the diametre of the mill the number of sharp edges, etc.
    - [jog(mm)] controls height when the mill moves in void
    - [xmin(mm)] and [ymin(mm)] are position on the machine coordinate axis of the bottom-left corner cutting region
    * The button move the spindle to the coordinates (xmin,ymin).

    On the top, the popup has the common mills that the fab uses. Each one loads default parameters for the milling proccess.

    Milling & Cutting Process

    Milling the Circuit with the Modela MDX-20 using our Mill Adaptor and not standar mill bits (conical bit). In our case normally need to use sandpaper to eliminate the mill burr on the copper surface.

    The board cutting we did with the laser cutter, it was easy and faster than the milling process. The copper layer on the cutting path was removed before this process. The parameters was Power = 100%, Speed = 50%, Frecuency = 5000Hz

    NOTE: Only the bakelite boards can be cut with laser. The glass-fiber boards can't be cut with laser.

    Welding the Electronic Components

    First the continuity of all the paths was checked. In one of the boards one of the paths was cutted by the sanding, and repaired welding a small piece of copper paper

    For place the Attiny44, tinned one leg of the microchipand the corresponding pad before welding it, this make easy the correct placement of this important component.

    Weld the two temporaly bridges, that will be removed after the programing

    Programing the FabISP

    I follow the academy tutorial to made this part.

    Downloading the Softwares

    Get all the softwares and drivers to your computer. In my case I did it in Ubuntu OS. On the ubunto Terminal and with the sudo active type in:

    [email protected]:~# apt-get install flex byacc bison gcc libusb-dev avrdude
    [email protected]:~# apt-get install gcc-avr
    [email protected]:~# apt-get install avr-libc
    [email protected]:~# apt-get install libc6-dev

    Connecting the FabISP

    Connect the AVRISP2 programer to the pinhead of the FabISP board and the microUSB port to the computer USB-port. If all is correct the AVRISP2 LED light will be green.

    Programing the FabISP

    Download the FabISP firmware (here), then unzip it in the desktop.

    Then go to the firmware folder (in my case is "fabISP_mac.0.8.2_firmware"):

    [email protected]:~# cd ~/Desktop/fabISP_mac.0.8.2_firmware/

    Then type "make clean":

    [email protected]:~/Desktop/fabISP_mac.0.8.2_firmware# make clean

    All was correct and the window looks like this:

    Then type "make hex":

    [email protected]:~/Desktop/fabISP_mac.0.8.2_firmware# make hex

    All was correct:

    Then type "make fuse":

    [email protected]:~/Desktop/fabISP_mac.0.8.2_firmware# make fuse

    All was correct:

    Then type "make hex":

    [email protected]:~/Desktop/fabISP_mac.0.8.2_firmware# make program

    All was correct:

    Checking the devices

    In the terminal check the usb devices type "lsusb":

    [email protected]:~# lsusb

    In the list will appear "Multiple Vendors USBtiny"

    Now remove the solder bridge and the 0-Ohm resistor (this could be removed with the desoldering wire)

    Final Products

    Some Tips

  • Check continuity in all the paths and shortcircuit problems with a multimeter
  • Start welding from inner component to the outer and left the big and bulky component for the end (the pinhead connector and the miniUSB port)
  • Fix the board before start the welding. If you don't has a 3rd hand vise, try stike on a pieze of paper or cardboard (A5 format is enought to manipulate it)
  • Clean the copper surface before the welding with a fine sand paper (#800-#1200) to eleminate the oxide layer.
  • At the end of whelding clean the remaining flux with isopropilic alcohol and a soft-brush
  • Weld in a ventilated place. The vapors liberated in welding are toxic.