OK, throw out everything you think you've learned about DIY PCB construction and I'll tell you how to do it the right way. lol jk.
OK what you do is you stick with SINGLE-SIDED presensitized board that you can get from ebay or MG Chemicals. Bear with me on this one. What you need is a florescent source, so you might want to get the light little unit with metal stands full price. You'll need a sheet of lexan its called (home depot), some printable transparancy sheets (and remember that laser and inkjet use different types, so get the right type for your printer...use inexpensive version and you tend to go through it so get a small stack). Ferric chloride solution is HAZMAT so obtain it locally by driving down to pick it up (as it costs $14 JUST for the additional hazmat on shipping). Also pick up a bottle of "developer" (its basically bleach concentrate). While you are running around pick up a box of disposable rubber gloves and some dollar-store foam brushes. Forget gerber and eagle for now. What I want you to do is download OpenOffice (its free) and use the vector drawing program on it. Set your grid to 0.1" and snap on. Build up circles and lines of the appropriate line width. Its parametric so you get your little connection circles just right. You might have to eyeball a little with stuff like DB9's so turn off snap and get it as close as you can (remember to turn snap back on). Remember to group things intelligently so you can duplicate things like DIP patterns and move them around like a pro. Don't get the bubbler. Again bear with on this one. This is how the pros do it. Get 2 glass casserole dishes for this and a small pyrex sauce pan. What you do is you manually transfer your master reference working circuit you have breadboarded out to OpenDraw (its virtually identical to Adobe Illustrator, but its free). if you do it this way, its a total shortcut. Instead of wasting weeks, months on learning stuff you'll never use, you just transcribe from the physical circuit to vector drawing program. And it works like the dickens. When you are ready to go to PCB load your transparency sheet and print. Cut it out with a pair of scissors. Wipe clean your lexan (maybe even wash it with your dishes so its nice and transparent). Set up your light source and get your presensitized board. OK now STOP! I'll give you years of experience right here. The actual transferring process is very TIME DEPENDANT. Follow exactly (like with a stopwatch) the time recommended by the presensitized board manufacturer. The reason why you use the full-price light unit and legs is because its also distance-dependant and radiance-dependant. You don't do it right you will have residual mask on the board that is unreparable (you just throw out the ruined board and get a new piece of presensitized) ***under-exposed***, or because transparency film isn't perfectly opaque, the light will work its way around and through the black traces ***over-exposed***. I have years of commercial prototyping experience and this is the distillation of what I have discovered. Its prohibitively expensive for the hobbyist to just go through supplies like I used to to find these things out. (Elance: Rosewoodind) OK, take the mask off the presensitized board (you can make smaller boards or get a large sheet and cut it down with a regular chop saw - abrasive blade, or band/jig saw) and quickly put the transparency fragment on it (****THE RIGHT SIDE UPPPP**** its possible to transfer backward so think it through first. Measure twice, cut once kind of thing) and then DROP the lexan onto it so it holds it in place. Registration isn't critically important here. But do it quickly/carefully all directly under the light source (turned off). Click you stopwatch and turn on the light source. AGAIN, exact timing according to manufacturer's instruction down to about seconds to tens of seconds. Throw one disposable glove on your left-hand (keep you right hand normal). When the timer expires, turn off the florescent (its the UV from it that actually transfers, not the visible light) so you can look at the finished transfer under regular incandescent for a bit. You'll notice you can see if it transferred right as it is a slightly different color than the unexposed traces. Premix the developer (and you can do this in a lit room, its not as sensitive as photography, just move with a purpose) directly to one of the casserole dishes. Just add water and mix well with a foam brush. Concentration isn't super-critical but measure. Temperature doesn't matter. Then drop the transferred board into the solution. Grab it with your gloved left hand and take a foam brush and wipe it periodically and gently, carrying away the dissolving exposed photomask to the rest of the solution. How you know you are done is you will have bright copper-clad everywhere except for your traces (this is normal) which will be a kind of green-blue color. Visually inspect. On your stove heat up your FC solution to very warm (this is warmer than lukewarm). Just touch your gloved left finger in periodically...get it just a touch hotter than hot bath water. Pour it carefully into one of your casserole dishes. Contrary to public opinion FC isn't corrosive, but when warmed up (and I'll tell you how to do this) it cuts through copper like a hot knife through butter. With that said, don't get any on you as it is a real irritant. Don't touch your eyes accidently, its like hot peppers on steriods. Just drop your developed board into the ferric chloride solution. Heat is the key here. If its room-temperature you can wait all day for it to "etch". If its very warm it only takes 10 - 15 minutes. Get a clean foam brush and manually wipe it across the surface carrying away the dissolving copper. You will know its done when the only copped left on it is under the photomask. remember, ZERO copper left on the paper-phenolic substrate...not even flecks. They will conduct. When you have fully etched take the board to your sink and neutralize with regular tap water, maybe even washing it a bit with soap. This stops the etching processes cold. You now have a perfectly etched DIY PCB. You are done for now. On Thursday, February 2, 2017 at 2:09:39 PM UTC-7, woody stanford wrote: > > OK, here is a short primer on how the good guys build things in a serious > hobbyist setting. > > The development is done in 2 main stages. Breadboarding, and PCB > construction (with presensitized board). > > The reason why the breadboarding phase is because the Inet is great, but > you can't believe everything you read on it. What you want to do is look on > the WWW for ideas and then breadboard them out. Once you get them reliable > and you undersand their operation, you can use the technique in your > personal projects. > > How you do this on a budget (as it is the Great Recesion) is you get cheap > Chinese breadboards on ebay for $5 a piece free shipping. Like here, > > > http://www.ebay.com/itm/830-Tie-Points-Solderless-PCB-Breadboard-MB102-65Pcs-Jumper-cable-wires-/231412564779?hash=item35e143832b:m:mlV4jkc4DpzzqjQsn-zO0-w > > The latest and greatest idea, the only downside is that it takes longer > than a week to get your stuff in but the price is right. You can also get > broken out sensors and the like for dirt cheap (basically mounted great > stuff the big guys use in smart phones and tablets). $5 per component is > typical if you know where to go. > > What you do is peal the backs off them an mount them to a 2' x 2' piece of > plywood you can get at Home Depot. And you are ready to rock. next step is > to find inexpensive, reliable power. A cool thing I've been playing with is > tablet bricks because they are reliable, ubiquitous and a lot of them > deliver a strong 1.0 Amp or 5VDC. Take your soldering iron, figure out the > GND and the +5VDC and you have comfortable power on the 1 amp range. As > always, PC switching power supplies are great too (just get a $5 DMM from > Harbour Freight and sacrifice its leads so you have a constant digital > power monitor....solder it on and wrap with electrical tape). > > What you do is you mount everything on your plywood. You take your > Fiscar's drill (with $2 high-speed steel Harbour Freight drill bits) and > you get a nice selection of dollar-store machine screws (and nuts) that > you've "tackle-box-ized". Shop the 99 Cent Store for these cheap tackle > boxes and pick up about a dozen of them to keep your stuff in (resisters, > relays, diods and voltage regulators). The trick with this is: mouser, but > listen...you can get premade kits for around $70 but they have less than $5 > worth of parts in them. What you want to do is put them together yourself > and when you get low on standard parts (like certain resistor values) you > just restock. All it takes is time to build these part kits, you put > together generic BOM (bill of materials) for your tackle box kits so you > have a nice selection of standard caps, diodes, transistors, MOSFETS, tiny > relays, optoisolators, MCU's like PIC's and of cource exotics like NEO6M's, > preprogrammed MCU's, and MCU6050's. > > Modern hacking requires attention to ESD (electrostatic discharge) because > a lot of your stuff has sensitive digital logic in it. The fix is basic. > Take a piece of silver solder and stick it in your ground power rail so > about an inch of its hanging out. Every time you get up to walk around > (where you accumulate chip-killing static) when you sit back down, just run > your finger unconsciously across the solder tail. You are now grounded. > Formal ESC with a wrist strap is ok too. But don't wire yourself to ground > btw as this can lead to you doing an impression of a light-emitting > resistor (an old joke but a good one); think about it electrically. > > OK, you BBB (in my case my BBBW), what you want to do is mount everything > to your plywood so when the wife says playtime is over, you can just put it > up. Also, claiming a second "junk drawer" in your kitchen is a life-saver > specifically for all your little tools and tackle boxes.What you do is you > get > > *** STANDOFFS *** > > To make standoffs you get a length of small-diameter ridged plastic tube > and you cut pieces off yourself (getting them from Home Hardware is > expensive) One of my little secrets. > > To attach your BBB to the plywood, mark the holes with a fine Sharpy, load > your bit in your Fiscars (at a slightly smaller diameter than the screw you > will use) and just sink a hole half-way through. Then take handful of > screws, a few standoffs and mount your BBB in a majestic location on your > plywood. Takes like 30 seconds and its secured for weeks of tinkering. > > Cut lengths of SOLID CORE insulated wire and strip the ends with a solid > professional grade wire stripper (they are cheap and so worth it). Now you > have all the wire you will ever need. First step with it is to wire your > breadboards power rails. Connect all the blue (or GND) rails with insulated > wire and what I do is run 3.3V on the left rail and 5V on the right rail > (because I'm working a lot of times with both BBB and TTL), but if just > working with 3.3V parts you can wire all your rails 3.3V to cut down on > confusion. > > You can do strain-relief by just knotting the power cord or whatever > through a hole in your plywood. Keeps you from jerking sensitive wires and > cables loose when moving around. > > THE PLAN > > OK, what you do is you experiment on your breadboards connecting > everything with wire. We all know how to do this. Get a complete working > version of the circuit(s) on your breadboard set up. This will become your > master reference for the next step: DIY PCB construction. > > > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/22bbdbdc-8346-42f3-b8a9-d3f005aad7e8%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
