Though there are many Instructables on some aspect of how to make circuit boards, this one is different. It's an instructable on how to make the things you need to make circuit boards, specifically, a flamboyant business card toy. Over the past six months I have set up fairly complete printed circuit board fabrication lab in my apartment, cheaply and safely, and I intend to cover all aspects of the process, from start to finish. Some of it you may have seen before, but here it is all in one place, with references.
The Business Card
All in all, I had to design and build an airtight etch tank out of laser cut acrylic, an SMD vacuum pickup tool, a reflow oven and temperature controller, refine the toner transfer process with a modified laminator, build a custom programming jig, and of course design, program and build from scratch every aspect of the thing I did all this for in the first place: my business card. In the end it was well worth the time to have the ability to make circuit boards appear in my hands in an evening.
The POV Business Card uses the classic persistence of vision optical illusion to flash your name and number in midair as you wave the card. Based on the PIC12F508, an 8-pin 6 I/O ultra-low cost microcontroller, it is entirely surface mount and extremely thin- it uses PCB laminate that is as thin as a standard business card. And at roughly $2 apiece in parts, depending on how good you are at sourcing components, they are cheap enough to hand out (to the right people).
But why go to all this trouble simply to make something to give away to someone I just met? Why not just have them printed up in an afternoon for less than 10 bucks at Kinko's? Why, because I want a card that would not get thrown out. A card that would embody exactly what I do, instead of clumsily trying to sum it up in an clever job title. A card that would get me places.
Picture the following scenario, if you will: you have just met someone who you need to know. In actual fact, they need to know you. Having exchanged introductions, "The Man," complete with dark suit and power tie, casually hands you his cloned, company-issue business card.
"Here's my card," he grins, knowing that you will impressed by his Ownership Of Card, or at least his Power Over Someone Who Owns An Embossing Machine .
Probably he expects to see you to scribble your number on a torn scrap of paper. But when you reach into your pocket and pull out your card, certainly he doesn't expect to see...your name glowing in midair, floating before his very eyes!
"It's called persistence of vision," you say, as you hand him your card. "I make these in my basement. From scratch."
You didn't even need to say another word; anything more would just be gloating. You can see the look in his eyes; he's already sold.
The tank should be airtight, with a secure lid, have an air inlet for a bubbler, to agitate and oxygenate the solution, and an air outlet to a house that will vent out the window. I also added a check valve to the air intake on the tank so that any exhaust gases stay out of the air pump. It should hold the board upright for the minimum amount of acid, and it should be opaque to light so that the solution does not degrade from exposure to the sun. However, I left one side clear so I can look at the board to see if it is done etching, and also because it looks cooler that way.
I designed my tank for a total volume of roughly 2 Liters, planning on filling it to only 1.6L to leave room for the air bubbler and hose, the board itself, and a little extra for a safe lip on the top. The 1.6L value was determined with the figure of .016 liters per cm2 of board area as reported here. Assuming a a, 8x10in double sided PCB with 50% coverage of 36 μm ("1oz") copper.
For reasons I'll elaborate on later, I chose to use Cupric Chloride (CuCl2) as my circuit board etchant. CuCl2 is corrosive to most metals, and a few plastics.
When researching the materials you plan on using, datasheets abound under the search terms "xyz chemical resistance." Understanding the properties of materials is critical in engineering something like this, so plan ahead. Finding out that a hose melted in your acid bath and contaminated the solution, and then having to fish out each and every little tiny chunk is no fun.
Very few things will survive highly concentrated acids forever. We aren't using anything highly concentrated,as far as these things go, but the effect is the same; it's acid-resistant, not acid proof.
The following materials are generally safe to use for the construction of the tank: