Automated Circuitry Making

This is the process of making electronics for the RepRap board. Primarily it is aimed at using a RepRap, combined with modified software to take an electronic representation of a circuit and create it as a physical object. There are varying levels of degrees here from copper only, to drilling, even component placement and soldering. A complete cycle electronics assembly machine would be an amazingly awesome and marvelous thing.

Obviously, all of these ideas require an actual RepRap machine as a prerequisite.

PCB Creation

All of these processes start with a blank copper clad board and the desired end result of a circuit board with the traces required for the board. There are a variety of ways we are examining for this approach.

Milling Head Route

This method would use a router attached to the RepRap machine and would selectively mill away the copper to separate the copper tracks from each other. The things to be investigated are:

• how accurate can the milling be done
• how small the area milled can be... at least between pins
• if a reprap machine could withstand the stress (if not, can you re-inforce it / reprap new parts?)

Etching / Resist Route

With this method you would be applying some sort of etch resist to the copper clad board by means of the extruder head. There are a couple ideas that we have been tossing around and are interested in pursuing. We basically only need one way to work. The etching itself is a simple process that is basically foolproof if one is using the correct precautions. Simple objects needed to do the lab work could even be printed with a RepRap machine (etch bath tray / bubbler / heater / beaker, stirring rods, etc.) This would make the etching process much simpler.

• these would be fairly easy to do and pose the fewest questions of if it will work.
• etching and semi-nasty chemicals are involved. not super fun.

Thermoplast Resist

This is the ideal route. You are using something that already exists in the form of an extruder. You simply need to find the right combination of plastic, extrusion rate, etc. It would be a very elegant solution.

• you already have an extruder, and practically no modifications required.
• you could print a holder for the board to get perfectly lined up 2 sided boards.
• the traces should be protected really well and thusly survive the etch process nicely.
• afterwards, the plastic could also serve as an excellent insulator.
• downside is that it may be tough to get the plastic off the board to solder.

ABS may end up being a material of choice in this process. It is temperature resistant (hot traces/soldering process), it has excellent insulation properties, and one of the most crucial: it dissolves in acetone. it remains to be determined just how easily this process occurs, however it is highly likely that the abs could be made thin enough for this to be simple. Also, if the ABS was left on prior to the drilling process, it might possibly serve as a nice guide for the bit before it hits PCB. It could also prevent/reduce burrs from forming during the drilling process. Afterwards, it could simply be cleaned off and the pads would be ready to solder.

Ink Resist

If plastic serves to be too difficult or expensive, then an ink resist process would probably work as an alternative. Instead of using an extruder print head, it would simply move a marker such as a Sharpie mounted in a holder that would draw the circuit onto the board. The holder itself could be printed out of RepRap parts and it would probably not even need its own controller... there would be no electronic parts.

• Sharpie pens are cheap and universal.
• you would also then have the makings of a drawing bot, useful for making art.
• the ink resist might not be of highest quality with pitting being an issue.
• it might be tough to find a pen of required tip size. testing needed.

Drilling the PCB

This is another task that is pretty mundane and repetitive. It also requires either extremely steady hands, or a drill press. Regardless, it is one that is well suited to automation. The holes locations and sizes are all known based on the circuit layout. The only thing needed to be done is to drill a hole at a certain coordinate. Drilling would be less stressful on a reprap machine. Especially if the hole being drilled was very small (1mm). This hurdle in the process should be fairly easy to clear. The problem it presents seems to be straightforward. However, perhaps Murphy will have something to say about that.

Placing Components

This task appears to be a pretty daunting one to automate. It deals with components, except some of them have multiple contacts and a variety of form factors. Things could be simplified with moving to a reduced component part, and a technology more suited to automated production like SMT (surface mount technology)

SMT Method

This method would actually take part after another, related process occurs. Surface mounted parts are most easily attached by using solder paste. Fortunately for us, we theoretically have one, so before the SMT parts are placed, the syringe goes over each pad and deposits the required amount of solder paste on each contact. Afterwards, the pick/place head deposits a component directly onto the solder paste which will ideally secure it in place until its ready to be soldered.

Normal Components.

I have no idea how this would work. Theres probably a way, if you can think of it... get ahold of us!

Soldering

I'll get back to this... also a tough one and highly speculative.
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