What exactly is rapid prototyping ?
Sometimes we get some great ideas; some ideas are forgotten due to it took too long to build other ideas.
But if we could just build our circuits as quickly as they came to mind, imagine how great that would be.
I recently learned about Circuit Scribe. This is some advanced technology that puts your best PCB layout application and laser PCB cutter to shame.
Circuit Scribe is a pen containing conductive ink. It's made by a company called Electroninks.
How long would it take to make a circuit using one 1.27mm pitch SMD microcontroller, which could blink a LED powered by a CR2032 battery ?
I believe that it would take less than 10 seconds. You wouldn't even have to worry about a resistor for the LED.
All you need is the microcontroller, a piece of paper, a LED, a 100nF capacitor, a battery and the conductive silver ink pen.
You don't have to wait for a PCB to be manufactured and you don't have to solder. Just draw the circuit on a piece of paper to the pins of the components - that will make the connection for you.
You can read their story here Circuit Scribe: Draw Circuits Instantly by Electroninks Incorporated — Kickstarter.
...I've heard some people are experimenting with creating printers that use conductive silver ink, but I do not know if they've made it to the market yet.
Combine with the Robox 3D printer, and you can have your final prototype quickly.
A group I meet with outside work is investigating PCB milling. It can also give good results in a shot time.
The various silver circuit solutions are mainly a novelty, but do have limited prototyping ability particularly with flexible circuits.
The big problem with either milling or conductive inks is that as soon as you move to any complexity and closely spaced pins on packages, you need tining and solder masks to make reliable circuits.
Four-layer PTH, tinned and masked boards are just a few days away, so no competition when you want a reliable compact prototype.
You're absolutely right. -When I needed a PCB here and now, I etch it myself. I can have a PCB within one hour using equipment for less than $10.
Sure there are disadvantages with the conductive silver ink, but there are disadvantages with all methods:
Time, cost, resistance, precision, unplated holes, components not mounting easily, etc.
Personally I am a "breadboarder". Disadvantages... Yes.. You can't stuff BGA chips down those holes (unless except for the K03, you'd probably be able to squeeze the entire chip into one hole).
Note: As I'm located in Denmark, I need to get the PCBs manufactured in another country; Hong Kong is my preferred choice. This results in it takes between 2 and 4 weeks for the PCBs to arrive.
The breadboard is also a bit safer/greener than the ferric chloride! Is that what you use at home? I gave that up loooong ago.
The PCB milling with CNC sounds quite nice. How does that work out in term of cost?
Services like PCB Train in the UK seem so cheap and hassle free...
I'm wondering if I won't use the conductive pen in schools where I do some electronics. That is very neat!
Where do you throw away your designs though? I don't have a silver bin
I use sodium persulphate. It's very clean. Though I do not do it, you can actually let it down the drain. What you can't do is to let the copper down the drain...
Sodium persulphate can be saved for later, if you don't saturate the mix, so you can keep it until next time you need to etch, even though several months pass.
I'll never use ferric chloride, it is definitely very messy and makes everything near it rust.
PCB milling cost, well.. it depends on the quality of the machine. You can get some cheap machines that makes a very imprecise job, or you can get something very attractive, but expensive: laser based machines. But in general, most of those you can afford, cannot make thin traces, because they're not precise enough.
The laser ones ... well, once you've bought it, you won't be using it often, because your electricity bill will suddenly rocket to the skies.
It might pay to buy a PCB manufacturer in China and move your prototyping there, if you're thinking about the laser based machine.
I guess you'll have to go to either the local recycling station or the local jewelry store to get rid of your design.
-Hopefully the jewelry store will pay you for the silver...
But one thing that you could do, is to either mill or etch as you use to, then drill, and finish up by making plated VIAs using the conductive silver.
I don't know if it will work, but those people who read this might want to try it out. It won't be excellent, as there's still the resistance to take into account.
Actually you could use the conductive silver pen for soldering copper-strands through the VIAs.
The PCB won't get too hot, so it'll be very easy to hold the copper-strand while you're "soldering" it with the conductive silver pen.
So... This means it opens up an entire new way of working. No more burning your fingers while soldering.
Now you just place your 1.27mm pitch LPC812 on your PCB, touch it with the tip of your silver pen, and you're done.
The resistance might even be lower than when using solder (haven't investigated this).
I have no idea how to unsolder the components, though, except from just tearing them of...
I've used such kind of conductive paste in the past.
But that was to repair a board with a broken pin chip, not to create fancy designs on paper