Printing electronics
The page is an attempt to collect, and perhaps direct, developments relating to fabricating circuit boards, electronic, and electrical components.
Contents
Motivation
- To truly print its own non off-the-shelf parts, the RepRap needs print its own circuit boards.
- Bruce Perens says we at least need macro-scale diodes to validate claims of changing the world.
- Just like the GNU C Compiler kicked off the software libre revolution, an open computer hardware fabricator is needed to start an open computer hardware movement.
Challenges
Unsuitable Conventional Processes
The conventional circuit board fabrication process is very involved, and for time and simplicity, fewer steps and chemicals would be good. Ideally, one shouldn't need a clean room to be able to use a RepRap to its full potential. That probably throws out photo-lithographic processes for smaller than macro scale. Also, particle acceleration takes too much energy to be reasonable, so ion implantation as a doping method is probably also unrealistic.
Hazardous Chemicals
Ideally, the chemicals used by the RapRap won't hurt living things. Eutectic alloys, etching chemicals, semiconductors, and dopants all should be carefully examined and selected to be non-hazardous, where possible. Some potentially dangerous chemicals used in the semiconductor industry include lead, cadmium, arsenic, and phosphorous. In some cases, such as using cadmium in photovoltaic cells, there may not be very good alternatives, so appropriate personal protection and recycling will be needed.
Circuit boards / Wiring / Traces
See also: Automated Circuitry Making and Plotting. Also, part of the Gada Prize is the ability to print at least three different materials, one or more of which is electrically conductive.
- In the spring of 2009 Rhys Jones modified the pinch-wheel extruder to drive flux-less solder through a thin tube with a nichrome heater wrapped around it.
- In the spring of 2009 Rhys Jones published his dissertation on New RepRap Materials.
- In the spring of 2010 three students from the University of British Columbia introduced the wire-laying SpoolHead.
- In the winter of 2010-2011, Rhys Jones ran some conductivity tests on dendritic nickel.
- In the summer of 2011, Rhys Jones satisfactorily printed a tin-bismuth-indium solder.
Electrical Components
- In the spring of 2011 Blogger user keltor suggested and Christopher Covington elaborated on graphite and resin resistors, which are used in conventional resistors.
- In the fall of 2012, Simon Leigh, Robert Bradley, Christopher Purssell, Duncan Billson, and David Hutchins published a process for creating a conductive, carbon-filled thermoplastic exhibiting piezoresistive behavior and the characteristics of a flex sensor and capacitive touch sensor printed with it.
Inkjetting
Included here as it may be the most effective method of depositing semiconductor material in solution.
Semiconductors
- In the spring of 2011 Kathleen Meehan proposed using II-IV semiconductors, in part due to easy wet-process creation. As direct semiconductors, they can also serve as light-emitting diodes (given a bandgap that produces visible-wavelength light).