Thursday, 9 February 2012

3D printing PCBs

Solder (see this for an example) has a melting point of 270C.
PET has a melting point of 250C.

If you could form 0.1mm cubes of each and arrange them in rows, then the "printing" process becomes a process of arranging row after row and layer upon layer into a finished (rectangular) shape - like a circuit board.

Subject the finished item to 240C and the solder and plastic will become soft enough to sinter to themselves while holding their relative shape.

The finished PCB won't be as tough as a regular PCB, but it would be possible to reuse them as they will separate with a sustained heat of 270C because of their different densities.

You obviously couldn't solder items to this PCB - they would need a mechanical contact to the solder.

Just make sure you have adequate ventilation!

Tuesday, 7 February 2012

the moist maker

I had an idea about how to connect a memory chip to the Broadcom BCM2835 for the Raspberry PI without the need to solder the connection.
The original comment is here and the blog entry is here.
I called it the "moist maker" because in the TV series "friends" that's the name Ross gave to the extra slice of bread soaked in meat sauce that went in the middle of the sandwich - a triple-decker.
I saw two chips and a plastic layer that goes between them - I thought that calling it a "moist maker" makes it easy to identify and reference.

I now realize that the scope of this idea is much greater than this one specific application.

Imagine circuit boards where most components are surface mount - through holes would only be needed where the increased pin density would require more precise component alignment.

Next, imagine a thin plastic electrically insulating sheet with conductive plastic pillars in it that conduct electricity from the component connector above to the circuit board below - the moist maker.

Finally a rigid transparent cover sheet that's molded or 3D printed so that it lightly presses the components onto the moist maker and holds them in place so they can't move and the electrical connection between them, the moist maker and the PCB is good.

The cover is held in place with clips on the edge of the PCB.

No need for soldering and if you no longer need the circuit, just unhook the cover and you can reuse the components.

The memory->CPU->PCB that started off the idea has more precise alignment requirements than other components and this would be possible by adding rectangular pillar into which the CPU, another moist maker and the memory chip fit. It would need to have pins that fit into slits/slots in the PCB to achieve the required alignment precision.

The other alternative to conductive plastic pillars is an insulating sheet saturated with carbon nano-tubes orientated perpendicular to the sheet surface.

As long as enough of them connect the item above to the item below without them shorting out adjacent pins or each other, it should work.

Once 3D printing takes off, the possibility of printing the multi-layer PCB complete with soft conductive component connections would open this up to hobbyists.

2013-11-07 update
You can now do a web search for "vertical conductive cloth tape adhesive" - let me google that for you:

I won't publish them here as there doesn't seem to be a manufacturers link available yet, but would it work for this application???