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PCB Fabrication
Overview, specs, links to other docs
Which process are you interested in?
HELP! –> See the Knowledge Base for processing issues/concerns/questions.
These guides is targeted towards End Users and PIs (Peer Instructors) who want to know about the standard fabrication process often employed at The Hive, either before they are certified or afterwards. It is not intended to serve as a technical manual for any of these three tools or the software that controls them; for those, see the individual tool SOPs. It is also not intended to serve as a complete list of all processes that can be achieved with this tool suite. It is simply a step-by-step guide to our two most basic and standardized processes.
Capabilities
The Hive has a suite of LPKF tools that enable students to fabricate 2-layer prototype-quality PCBs with fully-plated vias on campus. With additional setup, they can also apply soldermask and silkscreen for a production-quality finish, cut a solder paste stencil for part placement, and a reflow solder the components to the board. The tools have numerous additional capabilities beyond simple PCB fabrication, including 2.5D milling and exotic substrates etching. We encourage our users to explore new uses for the tools; however, as these options are beyond the scope of this document, if you’re interested in doing a non-standard process, we ask that you contact us beforehand.
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)
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.