Texas Tech University

Undergraduate Laboratories: Etch Room Policies

Printed Circuit Board Milling Room Procedures

Sign In Procedure

  1. Sign in to use milling room
  2. Indicate name, date, time of day, overall cleanliness of room, and number of safety glasses present. Make additional comments as needed
  3. Failure to sign in will make you personally responsible for the pre-existing condition of the room

Safety Procedure

  1. Wear safety glasses at all times
  2. Do not wear any loose clothing or jewelry into the etching room
  3. Never touch moving parts of machine
  4. Never inhale/ ingest copper particles created by the etch process (Make sure the vacuum is on and working properly)
  5. Use caution with bits, endmills, etc., they are very sharp
  6. Always have someone else present when using the etch room

Using The Machine

Materials Needed

  1. Gerber files
  2. Copper board (double or single sided), NO PHOTORESIST
  3. Tools (Bits, endmills, etc.)

Machine Care

  1. Do not use lubrication on the Teflon all-thread
  2. If machine is etching in the wrong place, tell the TA on duty
  3. Don't drop the tools
  4. ALWAYS double check depth of cut settings before running machine. Failure to do so could result in broken tools and damage to the machine

Initialize Machine

  1. Turn on all switches to the machine
  2. Connect the air hose to the air supply and turn on the supply valve
  3. Make sure the vacuum is connected and working properly
  4. Click on “initialize” in the IsoPro software
  5. Use “control J” to bring up the manual machine jog menu (Check the tool height before jogging machine to prevent breaking tools)
  6. Use the arrow keys to move head to a position in which you can change the bits

Setup the Machine

  1. Inserting and removing bits and endmills
    1. Push knob, located on top of spindle, down until it locks
    2. Turn knob CCW to loosen or CW to tighten
    3. Make sure tool is secure before running machine
  2. Setting carriage foot (depth of cut)
    1. The foot is used to determine a tools depth of penetration into the board
    2. The foot is set by thumbwheel located on carriage
    3. The desired depth of cut is dependent on procedure (see below)
  3. Setting vertical limits of tool carriage
    1. Top and bottom limits are set using the 2 pair of locking, threaded thumbwheels next to the spindle.
    2. Bottom limit should be set just below the desired depth of cut
    3. Top limit should be set to allow clearance and to minimize head travel distance (1/4” travel is sufficient)
  4. Placement of vacuum arm
    1. Bolt for vacuum arm adjustment is located on the arm clamp, located next to the spindle.
    2. The vacuum arm should be placed as low and close to the tool as possible. However, the arm should not be lower than the foot or so close to the foot that it restricts the up and down movement of the foot and tool

Board Milling Procedures

Place board on machine platform

  1. If you are using a new board
    1. Decide on a board axis. The board axis should halve the board and will serve as the axis for mirroring circuits on double-sided boards.
    2. Mark 2 hole locations .25” from each edge of board on the board axis.
    3. Place the .125” drill bit into chuck and move the head to the home position
    4. Move board and backing material in place under the drill bit
    5. Set drill depth using the foot. (Bit should penetrate the board and backing without hitting the platform: try using an extra backing board or drilling over the home position hole)
    6. Once board is in correct position, drill a hole on the marked spot (Use “spindle on” then “head down” to start the spindle and drill the hole)
    7. Place one of the fastener pins in the hole through the board AND backing material
    8. Drill the second hole in a similar manner, making sure the board and backing material are aligned as desired
    9. Place first fastener pin (with board and backing) in the home position hole
    10. The second fastener pin will fit into the slot running from the home position hole towards the back of the platform
  2. If you are using an old board – Place board on platform in as shown for that board in the database tool.

Import and Isolate

  1. Use the auto-detect feature (file menu) to import files
  2. Import pertinent files (usually *.top, *.bot, *.dxx or *.tap) selecting the proper settings (# integers, # decimals, units)
  3. Isolate top and bottom layers (tools menu)
    1. Use a larger endmill size first
    2. Verify that isolation has been achieved in ALL desired locations
    3. If the first isolation was not successful, isolate using the larger endmill and add a second pass using a smaller endmill (check “remove redundant data” box)
    4. Verify isolation again, and repeat step “c” if needed
  4. Use database tool if more than one circuit can be made from the board
    1. If you are working with a new board
      1. Click on data base tool and create a new board
      2. Use a short name for the board and scratch the name on the board (toward the front edge of the board)
      3. Carefully measure the board and enter the dimensions into the database. The board axis should halve the board and will serve as the reference for the “+X” and “-X” measurements.
      4. iv. Click on the placement tool and click on “place circuit” and place the circuit on the back, left portion of the board (leave a small space between the circuit and the edge of the board)
    2. If you are working with a board that has been used previously
      1. Verify that your circuit will fit on the board
      2. Click on the placement tool and select the board name (It should be scratched on the board)
      3. Click on “place circuit” and place the circuit in the available space (place the circuit as far left as possible)

Run Layers

  1. Refer to the table at the bottom of this document for suggested etch settings
  2. Drill layer
    1. Place the “milling tool” in the chuck and set proper penetration depth using the foot. (The milling tool should only make a small dent in the copper so as to give the drill bit a place to sit)
    2. Right click on drill layer and select “run layer”
    3. Enter the “spindle speed” and “traverse speed”, then click “ok”
    4. After machine finishes first run, complete steps a-c with desired drill bit size. (Drill depth should be set so that the hole is drilled through the copper board but NOT through the backing material)
  3. Bottom layer
    1. Jog machine out and place largest selected endmill in the chuck. Set proper depth using the foot. (Any endmill should penetrate the copper layer and reach only slightly into next layer of the board)
    2. Right click on the isolation of the bottom layer using the largest endmill, select “run layer”
    3. Enter the “spindle speed” and “traverse speed”, then click “ok”
    4. If more than one isolation was completed on bottom layer, complete steps a-c on the bottom layer in order of decreasing endmill size.
  4. Top layer (Skip this step if there is no top layer)
    1. Flip board over and place it on the fastening pins in the fastening holes
    2. Select and mirror layers which are to be on the top of the board and also the board outline layer
    3. Complete steps a-d in “bottom layer” section to finish board isolation
  5. Separating circuit from the board
    1. Place the “router bit” into chuck and set penetration depth (router should penetrate the copper board but NOT the backing material)
    2. Right click on board outline layer and select “run layer”
    3. Enter the “spindle speed” and “traverse speed”, then click “ok”

Sign Out Procedure

  1. Before you may sign out, you must clean the room.
  2. Place all tools in case and return them to their proper place.
  3. Pick up all debris from you boards, including paper and board trimmings.
  4. Make sure etch platform and surrounding area is clear of dust and copper shavings.
  5. Clean safety glasses and place them in the proper location.
  6. Unhook air hose from supply and turn off supply valve.
  7. You are responsible for the cleanliness of the room until it is checked and OK'ed by the next person.
  8. On sign out sheet, indicate name, date, time of day, overall cleanliness of room, and number of safety glasses present. Make additional comments as needed
  9. If you are the last person out, be sure to lock the door and turn off all the equipment.
  10. If you are leaving, and it is after 5:00 p.m., you must notify the Grad student in the computer room that you are done.
  11. Failure to leave the room in an acceptable condition can result in severe repercussions, including the lowering of your lab grade.

Suggested Mill Settings

Tool Type Application Spindle Speed (Rpm) Traverse Speed (In/min)
Drill bit, T1 m.t. Drilling, Tapping 60,000 20
.010” endmill Etch 60,000 20
.031” endmill Etch 40,000 20
.062” router Routing 40,000 15

Electrical & Computer Engineering