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.
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.