Re: Homemade PCB: Via advice

I'm not Brian, but I've used expresspcb.com for a couple of projects.
They have downloadable no-cost design software, and for $51 plus
shipping (I think it comes to a total of about $70) you get three
3.8x2.5 inch (exactly -- not larger, not smaller) double-sided boards
with through-plated vias. No solder mask.

They also have a variety of other services, like 4-layer boards,
silkscreen and solder mask layers, for more money.

The only thing I don't like about them is they're one of the two
reasons I have to keep Windows around.
--
Joseph J. Pfeiffer, Jr., Ph.D.       Phone -- (505) 646-1605
Department of Computer Science       FAX   -- (505) 646-1002
New Mexico State University          http://www.cs.nmsu.edu/~pfeiffer
                                     skype:  jjpfeifferjr

Compared to a commercial service, making it yourself still makes sense for a
hobbyist in terms of both time and dollars. Turn-around is about an hour,
compared to easily a full week or more. Materials and consumables for that
size board cost about $2 each. Plated holes are possible, but startup cost
is likely prohibitive: roughly $150 in equipment, ink, and electrolyte.
Solder and paste masks are also possible, but startup cost is even more
prohibitive, unless you already happen to have a laser cutter.

Compared to breadboarding, custom PCBs, especially homemade ones, can still
make sense. The time and effort to run error-prone and noisy jumpers is
roughly the same as preparing and etching the board. The PCB loses out if
you want to make a quick change after the fact. OTOH, breadboarding isn't
possible if you want to use even one surface mount part.

Yes, rolling your own is cheaper.

The turnaround time for the company I mentioned earlier (let me
mention I'm not affliliated with the company in any way; I've just
bought some boards from them) is two days (the only way the ship is
FedEx); this is nothing compared to the design time.

And my home-made PCBs, decades ago, were complete and utter crap.  I
was never able to get the etchant to take all the copper off before it
started eating through the resist.

I've seen people make good ones, and my hat is off to you if you can
get it right!


I'll agree with everything you say here.
--
Joseph J. Pfeiffer, Jr., Ph.D.       Phone -- (505) 646-1605
Department of Computer Science       FAX   -- (505) 646-1002
New Mexico State University          http://www.cs.nmsu.edu/~pfeiffer
                                     skype:  jjpfeifferjr

I've used both Advanced Circuits (http://www.4pcb.com ) and
Imagineering (http://www.pcbnet.com ) for prototypes.  Both are
execellent and the costs are very reasonable.  What I really like
about these services is that they offer a "prototype" service where if
your board conforms to a reasonable set of common specs, you can get
them done for a very economical price.  This typically applies to
2-layer, silkscreen, plated through holes, reasonable board size, and
up to 2 oz copper.  I've made a few boards that I couldn't use that
service on, but the bulk of the boards I've done match the specs of
their prototype special service.

Also, another great feature is that they both have an on-line quoting
service - enter the specs, and then get pricing on various quantities
- so you know right away what you are getting into with regard to
price.  No submitting engineering files and waiting around for someone
to get back to you.  Other services do this also, but the above two
are the ones that I have direct experience with.  Turn-around is about
a week in each case for protos.  You can get them faster, of course,
but the price generally goes up exponentially all the way to same day
turn around.

Regarding DIY PCBs, I've done the toner transfer method with mixed
artwork results as well as using photo sensitive boards and exposing
with light, fixing chemicals, etc, with execellent artwork results.
I've done both single-sided and double-sided.  I found the
photographic method to be far superior than the laser printer toner
transfer, though a bit messier.  In both cases, once you prepare the
materials, apply the artwork circuit to the copper clad board,
expose/heat, etc, then etch, and cleanup.  Note that doing a double
sided board is doubly hard because you need to ensure good alignment
and you also have the through-hole problem.  Don't forget you now need
to drill all those holes (not so easy) and then somehow deal with
through-holes (eyelets are extremely tedious and only work so-so).
After all that, you can use up the better part of a perfectly good
day.  And even after all that, the results (at best) were marginal -
nothing to write home about, and in some cases, the board has to be
scrapped due to process problems.

For these reasons, I'm willing to wait a few extra days and get a
supremely professional job done with an industry quality soldermask
and silkscreen, even when I only need a handful of protos.  I'm
certainly willing to pay their asking price for the 10 excellent
"proto special" boards I am guaranteed to receive from Imagineering in
a few days, as opposed to spend all day of my time and produce a
marginal one or if I'm having an off-day, maybe one for the scrap pile
and I get to do it all again the following weekend.  Woops, there goes
a Saturday :-(

-Brian
--
Brian Dean
http://www.bdmicro.com/

I offer the following to balance the viewpoints. Certainly there are skills
to be learned and a critical mass of required equipment and supplies is
required. They are rather small, however, and readily attainable to almost
everyone.


Carbide drill bits are specialty items. One inexpensive source is
http://store.yahoo.com/drillcity/index.html . Resharpened bits cost less than
$1 each. OTOH, you need to buy a few at a time. Expect to spend $20 or so on
drill bits. 24, 32, 40, 62, 125 mils are the sizes to get.

Dremels and Rotozips have 1/8" collets that take these drill bits. Some
folks mount them on drawer slides to guide them. I mounted a rotozip on a
small linear guide I snagged for cheap on eBay. CNC is better, of course. A
small drillpress can also work reasonably well. Drilling freehand with
carbide will only frustrate you and break the bits.

Toner transfer can be made to work. I get good results using Pulsar
products: http://www.pulsar.gs/PCB/index.html . I hear of good results from
glossy paper, and inkjet paper. I haven't tried those. Toner transfer can
make sense if you have ready access to a laserjet.

Photo-resist can deliver superior results. Pre-sensitized boards cost about
twice that of plain pre-clad. Laminant is not particularly expensive square
foot-wise, but it's difficult to find in small quantities. Exposure boxes
can be made from plain flourescent tubes and 1x lumber. You can also strip
the guts out of an old scanner and put in real UV tubes. Or just go the
old-fashioned way and mount a tube on a 2x4 frame. Developer and stripper
are common, cheap, and readily available as swimming pool chemicals.

I prefer toner transfer for my one-off work.


Start to finish for me is about an hour, from printing the artwork and
drilling the holes, to cleaning the sink and turning on the soldering iron.
There is value beyond simply dollars in the fast turnaround and the
continuity of thought preserved.

I'll leave it with one final thought. Holes are expensive, and unavoidable.
The rotary tool and its bondage, plus the bits, are the major capital
investments. Unplated holes and vias are without doubt a major PITA. A
clever person can build a small plating tank and power supply (5A DC into 20
milliohm) for not much more than $20. Anode bars and electrolyte adds
another $80. Conductive ink, if you can find it in very small quantities,
will cost another $50+.

Making your own is not for everyone. The obstacles are many, but small and
easily surmountable. They can be taken in baby steps, or all at once. I
doubt anyone really enjoys the mild tedium of making a PCB, but oftentimes
it makes sense compared to the alternatives, especially for
comp.robotics.misc.

[For the OP, the quickest way to "stuff" vias is to run a single unbroken
length of tinned 30 AWG buss wire through all the holes, and then solder
both sides. Clip off the stuff between the holes. You might get away with
these plugs under SO packages if you're good and careful, but SS and smaller
won't tolerate even the slightest bump underneath. You also have to keep in
mind soldering access when laying out your boards. The inside row on RJ45
jacks, for example, is accessible only from the bottom. All pads that
connect to signal traces need to be soldered. I take the time to solder all
pads on both sides for mechanical strength. For my needs, plating the holes
is the solution, not farming out the boards.]

"Mike Young"

Someone else had suggested zipping one single wire through all holes, simple
and clever idea. I managed to do my first board, had a couple of problems
with distance from traces and surrounding ground plane... I'm having no
problems drilling holes 0.038" with a bench drill, but you're right,
drilling one or two is different from drilling 40. Patience is a virtue.
I'm doing double side, the alignment came out perfect. The technique I'm
employing is to draw crosses inside big holes on the extremities of the
board, then drill it before exposing and then sticking the two
transparancies aligning the crosses through the holes.

I'll post more of my results later.

Cheers

Padu