Homebrew_PCBs

 

The www.das-labor.org/wiki/LaserExposer project is very neat.  The good stuff is in the second half.  I wish the page was all English so I could read it.

    

 

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Thursday, June 19, 2014 7:05 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Re: DLP for imaging photoresist

 

 

Hello all,
DLP imageing systems are a reality in the PCB manufacturing industry. Several companies do offer such systems: usually they have one or several heads mounted on a CNC machine, and they synchronize motion control & DLP control to achieve the right insolation of the photoresist. It allows a much higher throughput than LDI systems, even those who use several heads, and is more and more a good option for midvolume production. It also allows an arbitrarily high resolution compared to a static DLP projector, which has a very limited number of pixels, so you have to choose how to use those pixels, and thus between resolution & dimension of your PCB.

I've seen such machines at www.productronica.com in Munich ; I could try to find the references if some of you are interested.

Needless to say, those systems are very expensive, and not so easy to design ;)

I'd rather check the conference http://ehsm.eu/ and the talk about http://pcbwriter.github.io/ to see how well this thing works. There are other OSHW projects intended at PCB fabrication, but I'm quite curious to see if one will end up being really useful and powerful.
C.

 

On Thu, Jun 19, 2014 at 2:16 AM, stan_katz@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

 

This technology was reported for student use at Pomona College back in 2005:

 

https://www.physics.rutgers.edu/ugrad/387/388s06/film_deposition/Musgraves05.pdf

 

The cost of the setup was in excess of $5000 due to the use of a consumer grade DLP projector (which are still pricey) and a lab grade trinocular microscope.  The article claims even an ordinary stereo microscope can be used for less demanding applications. I haven't taken a look, but I'll bet the name(s) of one or more of the principals presenting the above paper are on one or more patents that are held by Maskless Lithography Corporation.

 

I hope there are talented folks in this group who might start thinking about putting together a DLP system on a hobbyist's budget. Up until now, the only hobby systems, presented in this group, not requiring some sort of mask, e.g led/laser flat or cylinder photoplotters have been built by individuals with machine shops at home.

 

 

> 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

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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>
> I didn’t know laser engravers were as low as $300. Do you know a link?
>
> Jeff
>

>
> *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.
> ******
>
> ---
> This email is free from viruses and malware because avast! Antivirus
> protection is active.
> http://www.avast.com
>
>