HOW TO SERIES PART 1- PCB STUFF
PCB's at Home: (circa spring break 2011)
By Ian Campbell
The first step in generating home made PCB's is having a need for one in the first place.
If you are like me and suffer from being a mad/silly scientist and want to make a mess in every room in the house, these instructions can help you out.
The trade off in prototyping on copper clad is interesting. For me, breadboarding can turn into a huge hastle.
I tire of wires running everwhere and forgetting what pin is what. This is because I'm generally a really sloppy person.
The PCB prototypes might generate more waste, however the chance for error is changed from frying chips because of
"missing the node" when plugging something in... into error based on computer glitches and printing things backwards.
If you're really hip you could figure out how to socket all your resistors and caps.
Here are some photos and explanations of the process:
ACETATE:
If you are like me you don't have a job where you can "borrow" stuff like this. I'm using copier transparency in a lazer printer (don't tell my mom). Sadly 100 sheets of Acetate transparency paper costs 35 dollars. Shell it out baby!
CAD it up:
I used Eagle. This PCB software is free, and generates the PCB artwork from a schematic you draw up. This one has a decent auto router, if you are willing to futz with it. If you can use parts that are already in the libraries!
This program has a bit of a learning curve, however there are much more qualified geeks than me who have 10 or 15 youtube tutorials that will get you on your feet in a weekend or so.
When I get my schematic going, I turn off all the layers except the ones I need and export a monochrome 600dpi image which I then print out at 12 percent the original size (I use PSP5 but hey I'm old)
Print It!
Correct Orientation?
Can you see the hand of the artist? If you get right brained enough while doing this, you will either mirror the image when you shouldn't have, or not mirror the image when you should have. I don't know what side of the paper gets the toner on your computer, but make sure you dont have to flip over you DIP and solder it to the wrong side...
Toner Transfer:
You will need some copper clad (maybe fr4 board?). Comes in 1oz and 0.5oz, single and double sided. Pick your poison.
Ironing copper clad is a bit weird. I like it when I burn my fingers. Start with a lightly scuffed clean surface.
I try to get the copper hot then real quick stick the toner to the hot board. Once again youTube has a bunch of
videos featuring the "Toner Transfer PCB method" or whatever. Apply plenty of heat and pressure and avoid blurring.
This may take a few tries so maybe have the laquer thinner/ acetone handy with a paper towel. Feel free to ruin your room mates
ironing board.
FeCl Mess:
This is stuff from radio shack. You can presumably get this in whatever form you need.
I have seen Iron Chloride that you mix into solution yourself, as well as these bottles which are pre mixed.
You may have experience with Muriatic Acid (HCl for the pool) so if you know how use that,
I melted a few things with Muriatic Acid and that stuff is totally toxic, dangerous and disgusting (but it makes a cool green foam).
The FeCl is only slightly better, but you can pour it down the sink when you've used it all up.
(Copper ions are lethal to invertibrates) Can't remember how much this stuff costs.
Somewhere between 10 and 20. If you save it, should be good for a long time.
Here laid out is the stuff for your etch tank. I've ruined some tupper ware I found in the back of my parents cupboard. Aw Jeez.
The toner will be your resist for the etch process. If you have smeared a little, you can scrape it off with a razor blade. I like to make sure everything looks good at this stage before moving on, as opens and shorts in the finished product are a bummer. Some experience with this can dictate what you can get away with in the cad phase. Wider traces and wider spacing help, but you can't always get them perfect. I have successfully made a 28 pin SSOP converter to DIP using this method, so you can too!
ETCH TIME:
Throw that board into the acid tank and etch it for 2+ hours. I've had weaker solutions take all night to etch. Agitate the mixture and do it at higher temperature to increase the reaction time. If you haven't had a glass of wine yet, now is your chance, or maybe put on your favorite Katy Perry limited edition Vinyl?
Check for defects like this one. This presumably was the result of a greasy finger print that resisted the etch in places I didn't want it to. Could be solved with some careful X-Acto-ing but usually I make 2 or 4 of these things at a time, so this guy hit the garbage.
Garage Type Tools:
You will need to clean the boards when they are done etching, then drill the holes. This time I used Laquer Thinner and a set of tiny drill bits, a drill, and a hand saw to get the board into shape. Do this somewhere where saw dust is acceptable (kitchen table?).
EE Workbench type tools:
Use stuff like this to attach your parts.
I hope you already have this stuff, because this stuff is awesome.
Hey not bad. Now you can hunt bears with a lazer beam, or whatever this thing does...
This guy is a band limiting filter for some audio signals.
Did you get this far and regret having to drill 100 holes? Why not go SMT???
I got this stuff for mostly cheap from china. Took a long time to ship but the price was right, and the values are almost within 10%. I think the caps were advertised at 20%. Kits like this range from 10 to 20 on eBay.
Did you get this far? Email: ian@friendsofcampbell.com for details