pcb-help_fab

This is an old revision of the document!


I’m ready to have my board professional fabricated. Do you have any recommendations? We don’t officially recommend any of the following fabrication houses. All of them have positives and negatives.

Some additional notes on board design and fabrication:

  • Slots are hard in this process. Please consider using a single drill hit that’s wide enough if possible. If it’s unavoidable, the current recommended option is to use overlapping drill hits.
  • Plating is typically avoidable by making vias with a diameter of 40 mil (1 mm). A standard 0.1” header pin can then be pushed through and soldered on both the top and bottom.
  • Higher polygon isolation will reduce the chance of bridging to a plane during assembly (since we don’t really offer soldermask). However, it will also increase etch time.

Slots
Substrate thickness

Fabrication

Process specifications
The Hive's PCB fabrication tool suite has the following capabilites:

  • Substrates: FR4, Rogers materials, polyamide, among many others.
  • Copper thickness/weight: No limit, other than processing time.
  • Trace width (minimum): 2 mil (0.05 mm)
  • Trace pitch (minimum): 1 mil (0.025 mm)
  • Drill holes (minimum diameter): 6 mil (0.15 mm)
  • Slot: yes, use overlapping drill hits
  • Plating: yes, standard processing time of 3 hours will plate approximately 12.6 um of copper

Can I add soldermask or silkscreen?
We have the capability to apply soldermask and silkscreen, though we do not recommend attempting this process - it's time-consuming, UV- and temperature-sensitive, and unnecessary to a complete circuit board. If you need soldermask or silkscreen, consider sending your design to a professional fabrication facility.

For those who would like to attempt this, instructions are available on our mask and silkscreen page, as well as in the “Manuals/Instructions” drawer next to the tools themselves.

Is there a recommended DRC/CAM file I can use?
Yes!

Do I have to be with my board during the entire fabrication process?
Yes! You must be present for the entire process. This is for safety reasons. PIs have the authority to cancel any unattended boards. You may, however, leave the space if and only if you leave a note with a phone number and accept the possibility that something may happen to your product while you're gone (because PIs are not watching your process).

How long does it take to make a board?
It depends on the size and layout of your board. A small board with no electroplating (i.e. no vias) can easily be made in under an hour, while a very large board with lots of copper removed can take over 4 hours not including electroplating.

How long does electroplating take?
Between 2 and 3 hours, regardless of board size. This will plate between 8-15 um of copper onto your surfaces. Less than this processing time can cause unreliable vias with variable thickness of the plating.

Can I somehow reserve time on the equipment?
Yes! Although you are not required to, we highly recommend that you do as it guarantees equipment priority. You may reserve time up to 96 hours in advance though SUMS. See the SUMS Guide for more details.

  1. Go to sums.gatech.edu and login (button is on the top right of the screen).
  2. In the main toolbar on top, on the right, click “Set Active BG/EG”. Make sure your Billing Group is “Interdisciplinary Design Commons” and your Equipment Group is “The Hive”.
  3. On the main page, locate the Schedule section. Under the drop-down menu that says, “My Schedule - Select a tool to schedule time”, select the tool in question. Note that you cannot reserve time on a tool until you have completed training for it.
  4. Click and drag on the calendar itself to reserve time. Release the mouse button to bring up the reservation screen. You must enter a description in order to reserve time! Click “Save” to save the reservation.

We highly advise you to schedule time on all the tools you’ll need, i.e. if you’re fabricating a standard board, you should reserve time on both the Plotter and the Laser. If you do not, and someone schedules time on only the laser, they have priority on the tool.

Reservations are limited to the following:

  • Non-PIs (i.e. those who are not volunteers at The Hive) may schedule a maximum of 4 hour block per tool per day during The Hive’s open hours, and up to 4 days in advance.
  • PI’s may schedule up to 8 hours per tool per day, up to 7 days in advance.

Do the tools have additional capabilities?
NOTE: The following capabilities are allowed in the spec of the tool, but we do not support these functions, meaning that our PIs and MPIs do not have experience with them, so you will be on your own if you attempt any of them!
The ProtoMat has the capability to do aluminum and plastic 2-dimensional milling. The ProtoLaser can etch a very wide variety of substrates and films. The electroplater has the ability to do tin plating (though we don't carry the necessary solution by default). We also have the LPKF ProConduct system that enables manual electropating of individual vias for RF PCBs (proceed with caution here).

The full suit includes the following:

  • LPKF ProtoMat S103 (datasheet) - drilling, milling, and routing
  • LPKF ProtoLaser U4 (datasheet) - etching, cutting
  • LPKF Contac S4 (datasheet) - electroplating
  • LPKF ProMask (datasheet) - Soldermask
  • LPKF ProLegend (datasheet) - Silkscreen
  • LPKF ProtoPrint S (datasheet) - Solderpaste stencil holder
  • LPKF ProtoFlow (datasheet) - Reflow oven
  • LPKF ProConduct (datasheet - Plating for RF applications

See our Standard Operating Procedures page for further details.


Process Specifications and Tolerances

If you’re board passes OshPark’s specs (OshPark .dru file), it can be made using our process (see their website for details). However, our process can, in fact, go beyond that in some ways.

Specification Minimum/Theoretical Recommended
Trace width 2 mils (0.05 mm) 10 mils (0.25 mm)
Trace spacing (“pitch”) 1 mils (0.025 mm) 6 mils (0.15 mm)
Polygon isolation 10 mils (0.25 mm) 30 mils (0.75 mm)
Drill hit 6 mil (0.15 mm) 15 mil (0.4 mm)
Drill X/Y resolution +/- 0.01 mil (0.25 μm)
Drill repeat accuracy +/- 0.2 mil (5 μm)
Laser repeatability 0.08 mils (2 μm)
Drill hit 0.05 mil (1.2 μm)
  • pcb-help_fab.1610594182.txt.gz
  • Last modified: 2021/01/13 22:16
  • by benh