As Brooks pointed out, these days a PCB fabrcation house
can do it at a lower cost than you can at home.
JeffM
Lower cost? Some copperclad, a sheet of Press-n-Peel or glossy paper
and a few cents worth of etchant and toner does not add up to $33+.
I could 'pay' myself twice the minimum wage and still be ahead.
Tim Auton
Sorry to hear you're only making twice minimum wage.
You're not factoring in that
the 1st time it's not "a few cents worth of etchant";
you have to buy an entire bag or a whole jug (+hazmat shipping ?).
You also didn't mention the basin.
(Most experienced folks would heat the solution;
Harrison rig shows a Pyrex dish.)
Surface prep, ironing, remove PnP, inspect,
correct flaws in toner deposition, mix etchant, heat etchant, etch[1],
drill for non-SMT items[2], remove toner, inspect, clear flaws,
dispose of (or re-bottle) etchant, clean up work area.
It may be a breeze the 2nd time;
the 1st time, it's a good chunk of a day consumed.
If you're using clay-covered paper, add even MORE time.
The 1st time is where you learn all the little tricks
and most folks don't want to do it themselves a 2nd time.
.
.
[1] If you don't have a mechanical agitation system,
you have to stay close by and do it manually.
[2]The whole *vias/PTHs* thing is a discussion all unto itself.
-----------------------------------------
(Just for the sake of accuracy, and maybe more "completeness", for
people who might need to decide what the best way to go about getting a
pcb made is, in their particular situation
The etchant CAN be dirt cheap: I now use two parts common 3% Hydrogen
Peroxide plus one part common Muriatic Acid (i.e. 20-something%
Hydrochloric, IIRC), which are both very-widely available, in small
quantities, very cheaply. [Using a fresh batch, each time, it's less
than $0.25 per board; maybe way less.]
It etches a 1oz board at room temperature in about five minutes, with
hand agitation (i.e. a hand in a disposable latex glove, gently wiping
surfaces of PCB with a small wad of paper towel). [Less than $0.10 per
board.]
I etch in a cheap plastic food container from WalMart: [Less than $1.
Divide that by the number of boards etched in your lifetime.]
Copperclad, even pre-cut to specs, within .01", is extremely cheap,
from the right vendors. [Certainly less than $0.50 per board, for,
say, 4"x6" or 9"x3", 1 oz, 2-sided, .082"; and WAY less for
cutting/sizing to specs within +/- 1/16".]
Surface-prep requires an abrasive nylon pad (e,g, a "Scotchbrite" pad).
[Reusable for at least 20 boards: Less than $0.10 per board.]
I don't use "Press-n-Peel" (PnP). It's just one more thing that I
can't get locally within 10 minutes, and is kind of pricey, too. I run
glossy inkjet paper through an old laser printer. Even in very small
quantities, I think it's less than $0.10 per sheet. (And you can buy a
whole truckload of old laser printers for $50.) My old LaserJet 4's
toner is super-expensive, around $80 or more, for something like 4000
sheets printed. Assuming only one board's patterns are printed per
sheet, that's about $0.02 per board.
And I don't believe that using clay-coated (i.e. "glossy") paper would
take MORE time than PnP, even for 1st-timers. Not at all. And I think
that the results, using glossy paper, are AT LEAST as good as those
with PnP.
The TOTAL time required COULD be as short as 20 minutes from "pattern
on computer screen" to "start soldering components", for simple boards
(i.e. with very few drill holes; Surface mount would be even better.).
Drill bits: I use used, "re-pointed" carbide bits, purchased in
quantities of about 100 at a time for about $25.00. If my drill press
(and my technique) don't break too many, we can probably say way less
than $0.25 per board.
Well, I probably forgot to mention some of the replenishable materials'
costs. But you can probably see the trend and do the math.
For anyone who wants a prototype or one-off PCB, or even a small
production-type run, my method is obviously way less expensive, even
just in terms of out-of-pocket expenses, even (or maybe especially) the
first time.
Each person (or their company) would have to calculate their own time's
value, to them or their company, to see if a board-house makes more
sense, at that time, for their needs and their situation. HOWEVER, if
you need a pcb or two, VERY QUICKLY, e.g. if an engineer's or
technician's time is going to be more-or-less wasted until the board is
in hand, then you had better also take that cost into account. Delays
can be detrimental or costly in many other ways, too. So you might
also have to compare the cost of the time spent doing a toner transfer
pcb to the large "express turnaround" fee that a board house would sock
you with, and then still take a day or more to get your pcb to you,
plus the cost of that delay.
Regarding the "1st time" or startup costs, and the extra time required,
etc: Most of the costs were covered above, except, of course, for
things like driving to supplier locations (or ordering on-line), which
also takes some time (and money), as well, plus the "opportunity cost"
value of a person's time.
You are probably correct about investing a whole day (or at least a
half-day), the very first time you attempt to make a toner transfer
PCB. (And if someone is setting up to be able to make small
production-type runs, it might be longer yet.)
BUT, hey! How does that compare with the 1st-time costs, and cost of
time spent, when using a PCB-fab vendor?? Worst-case might be someone
who's never done either method. Are you going to take into account the
cost of the pcb-design software they would need, and the time to learn
it, to be able to generate the files required by the pcb-fab guys?
(Toner transfer files could be created with MS Paint; probably very
quickly for small or simple boards.) Even for those already owning,
and experienced with, pcb-design/layout software, just finding a pcb
fab house to try, reading their website, readying the files to send to
them, emailing them, getting a quote, arranging and sending payment,
etc, etc, would probably eat up a good half-day, and maybe more,
especially the first time. (And, for those people, the artwork for
toner transfer might already be done and ready to print.)
You are certainly right about plated-through holes, and vias, being a
HUGE problem, for all DIY pcb-making mehods. It uses up a lot of board
space, to have to make pads on both sides, for example, for each via.
And then a wire has to be soldered through them (or special eyelets
crimped in). And I do greatly-dislike not having plated-through holes.
If I use, for example, a DIP socket on the top side of a board, then I
basically HAVE to approach every one of its pins with a bottom-side
trace (or make a "via" pad nearby), or else they can't be connected by
soldering. And if board real-estate is getting tight, all of that can
be a REAL pain.
SO, it should be noted that, if making a choice between DIY pcb-making
and using a board house, then the PCB LAYOUT, itself, would have to be
compatible with DIY limitations, for DIY to even be an option. For
existing board layouts that were intended for professional manufacture,
DIY is not likely to be an option, without re-layout work, except for
the simplest of boards.
And, of course, most people limit DIY pcb-making to single or double
sided boards. SOME people do make "multi-layer" pcbs. But they
generally just use very thin pcb stock and then glue the layers
together. Seems like another "can of worms", and more "hoops to jump
through". Never tried it, although I have been very tempted, at times.
OK. Sorry to have blathered-on for so long, about all of that!
I hope I didn't sound too biased, and that I wasn't actually unfair or
inaccurate in my comparisons, et al.
The bottom line is that I think that, in general, there might be times
when DIY toner transfer pcb-making could make more sense than
out-sourcing, and wanted to try to shed some light on some more of the
factors that might be involved, for someone who might be faced with
choosing among the available methods for coming up with a printed
circuit board.
(Whomever mentioned my website, in this thread, thanks!)
Regards,
Tom Gootee
tomg at fullnet.com
http://www.fullnet.com/u/tomg
-------------------------------------------
