Homebrew PCBs

On 6/20/2014 3:11 PM, 'Jeff Heiss' jeff.heiss@... 
[Homebrew_PCBs] wrote:
>
> I didn\u2019t know laser engravers were as low as $300.  Do you know a link?
>
> Jeff
>

Hello, Jeff and the group--

I don't have a link, but again IIRC it was a homebrewed job and that was 
the builder's component cost.

Commercially-available (Chinese) engravers are available under $500 
($479 OBO) on the auction site:

http://www.ebay.com/itm/NEW-USB-CO2-LASER-ENGRAVING-SPECIAL-BUY-CUTTING-MACHINE-ENGRAVER-b8-/221270094985?pt=LH_DefaultDomain_0&hash=item3384b9b489

...Or as a TinyURL:

*http://tinyurl.com/kt8lu24

Please accept my apologies for any confusion.

73--

Brad  AA1IP
**************************
*
>
> *From:*Homebrew_PCBs@yahoogroups.com 
> [mailto:Homebrew_PCBs@yahoogroups.com]
> *Sent:* Friday, June 20, 2014 12:30 PM
> *To:* Homebrew_PCBs@yahoogroups.com
> *Subject:* (long) Re: [Homebrew_PCBs] Re: DLP for imaging photoresist
>
>
> On 6/20/2014 5:17 AM, Clement Quinson clement.quinson@... 
> <mailto:clement.quinson@...>
> [Homebrew_PCBs] wrote:
> > Well as I said, I am very interested by that kind of equipment, and
> > will meet in approx one week those guys during a OSHW conference.
> > Hopefully we'll chat, and I would like to contribute to their project,
> > by reproducing their experiments, and also helping with documentation.
> > That could be a neat thing to push forward an efficient, "unified"
> > OSHW project like that !
> > C
> Hello--
>
> I recall seeing a description of a "direct laser projection" PC-board
> exposure system that
> uses an inexpensive ($300) laser engraver. You cover the copperclad
> board with several
> coats of flat-black spray paint and then use the engraver to vaporize
> the pain and expose the
> copperclad for etching.
>
> I couldn't find the exact reference, but here's one that's similar:
>
> http://www.youtube.com/watch?v=OTGZcY7WyYI
>
> While we're on the topic, I wonder whether anyone has experimented
> with using a 3D printer to deposit plastic resist on copperclad? I did
> get a few comments, but to my knowledge, so far no one has tried it.
> You'll find my e-mail description of the process appended below.
>
> 73--
>
> Brad AA1IP
>
> *****************
> Hello--
>
> I'm posting John's thoughtful comments (which I very much appreciate) 
> below
> and inserting my responses. My original posting is appended.
>
> On 5/6/2014 11:39 AM, John D'Ausilio wrote:
> > Responses inline (since there are so many questions
> >
> >
> > Questions and caveats:
> >
> > --Component pads' shapes may not translate well from Gerber code--
> > i.e., several overlapping passes would be needed to make large pads.
> > In general, printers which extrude ABS or PLA use a tip with a 0.4mm
> > hole. The resulting "noodle" is generally around 0.5mm wide and
> > roughly circular in cross-section.
>
> Hello, John and the groups--
>
> Depending on the "squishdown" factor, a 0.5 mm wide noodle might produce
> a 0.020 inch wide trace. If the noodle doesn't become a semicircle upon
> contact with the copperclad surface, the trace width would be narrower.
> > --Extruded plastic may not adhere well to copper.
> >
> > --Unetched copperclad board may need to be heated for best trace
> > adhesion.
> > Getting the plastic to adhere to the build platform is challenging.
> > ABS is usually printed on a heated metal plate covered with Kapton, or
> > lately on a heated glass plate sprayed with cheap hairspray.
> > I can try clipping some copperclad to my build plate and see what
> > happens ..
> Copper's higher thermal conductivity might be our friend. Imagine
> using a couple of Dale RH-50 chassis-mounted wirewound resistors
> clipped to opposite sides on top of the copperclad board. The resistors
> could provide auxiliary heating.
>
> > --Dimensional issues: how accurately can a 3-D printer locate 
> coordinates
> > at distant extents of a large layout?
> > Machines with orthogonal mechanics have the same accuracy at all
> > points on the build plate. Machines with delta mechanics lose
> > resolution towards the edges. The vast majority of hobbyist printers
> > are orthogonal.
> Excellent!
> >> --What's the narrowest (or widest) trace that can be extruded?
> >>
> >> For general object printing the goal is to squash the first layer into
> >> the build plate, reducing it's diameter and spreading it out.
> >> Realistically you could probably achieve around 0.55 or so with a .4mm
> >> nozzle
> Converting 0.55 mm to inches would produce traces a whisker under .022
> inches in width.
> > --How accurate can the copperclad board be leveled on the printing 
> stage?
> >
> > We already level our platforms, assuming the copperclad is
> > dimensionally stable over 20C-100C range (we usually heat to 100C for
> > ABS) then leveling shouldn't present a problem.
> One online source lists "...G-10 and FR-4 are rated at 285 degree F
> continuous operating
> temperature..." but I didn't locate a value for horizontal coefficient
> of expansion.
> >> --How well do various types of extruded plastic resist commonly-used
> >> copper
> >> etching solutions?
> >>
> > That's the $1000 question .. almost all printers in hobbyist use will
> > print ABS or Polylactic Acid (PLA). I don't etch boards so I have no
> > chemicals here, but I'd be happy to send you some samples.
> The "go to" source for chemical resistance is apparently Cole-Parmer:
>
> http://www.coleparmer.com/Chemical-Resistance?referred_id=11033&mkwid=sJFDnHw4J&pcrid=12430988319&kw=%2Bchemical%20%2Bresistance%20chart&mt=b&pdv=c&gclid=CLC49vnUl74CFe99OgodbF4A_w 
>
>
> ...Or TinyURL...
>
> *http://tinyurl.com/jwnnbk2
>
> Commonly-used etchants include ferric chloride, hydrochloric acid,
> ammonium persulfate
> and vinegar.
>
> ABS resistance:
>
> Vinegar A-- Excellent
> *
> Ferric Chloride A-- Excellent
>
> Hydrochloric Acid 20% A-Excellent
>
> Ammonium Persulfate A^2 -Excellent (2 = satisfactory to +120 F (+48 C)
>
> I couldn't locate a reference for polylactic acid's chemical resistance,
> but I'm pressed for time.
>
> -Could you use different colored extrusion plastics to mark, say, power
> and ground traces?
> > Not easily .. it's very challenging to print more than one color at
> > the same height (you would need more than one nozzle, and a way to
> > move them away from the piece so the unused one didn't plow into
> > existing plastic)
> Okay-- variously-colored resist would be a bonus.
> > --Could you leave the extruded plastic traces in place as a solder mask
> > and clean the plastic away only from component pads requiring soldering?
> > All of our plastics melt at 220C or less .. not compatible with
> > soldering temps.
> That might not be a problem if the plastic melts short of contaminating
> the solder
> joint. Careful removal (mechanical abrasion?) of the resist on the pads
> would
> be necessary.
>
> Further comments from all are welcome!
>
> 73--
> Brad AA1IP
> ********************************
>
> Original posting follows:
>
> Excuse the somewhat off-topic nature of this posting, but
> I'm picturing the Glowbug application (i.e., custom component-terminal
> boards) along with QRP and general circuit-design applications.
>
> Has anyone in the group used a 3-D printer to create one-off PC boards?
> Consider this as the inverse process of removing copper via a
> CNC milling machine.
>
> ***********
> Here's how the process might work; unfortunately, I don't own a
> 3-D printer, and thus the following description is theoretical and
> riddled with caveats.
>
> 1.) Create a PC-board layout using any of several available tools.
>
> 2.) Translate the layout program's output into an X versus Y format
> understood by the 3-D printer.
>
> 3.) Extrude plastic to "draw" the layout's traces on a sheet of copperclad
> board.
>
> 4.) Etch the board.
>
> 5.) Remove the plastic traces and drill holes in pads to accommodate
> through-hole components' leads; tin-plate the board if desired.
> ******
>
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