Homebrew PCBs

Larry and others,
      If you print onto a sheet of plastic with an inkjet and
put it into the acid for us. I am out of acid right now. Let us
know if the inkjet ink holds up! If it does then the idea is 
valid. I remember a guy from Texas asking me about printing directly
onto copper. I am overwhelmed with projects right now and it has been
too hot this summer. I burned out trying to finish the Morph!

                                              Cranky




--- In Homebrew_PCBs@y..., "Larry Edington" <ledington@a...> wrote:
> The problem with scratch and etch is the same as milling. Users 
must have a toolpath calculation program to 
> generate the outline toolpaths. In practical terms, that's 
expensive for robust software that can do small trace
> pitches. 
> 
> Outline paths also have the problem of "islands" of varying sizes 
which can cause a lot of problems
> for high speed boards. I don't think you could practically route a 
differential trace pair with isolations. There would
> be an enormous amount of rubouts required to clear all the copper 
between the traces but keep the traces at the 
> proper spacing and width for the correct impedence. One tiny hair 
of copper running along between your traces
> can really mess up the signalling. I wouldn't even try an LVDS bus 
with isolation.
> 
> Sure, Eagle can do outline paths but not everybody uses Eagle. T-
Tech's Isolator Pro does excellent toolpaths
> but is expensive!. KellyCam generates pretty good toolpaths but 
sucks as a CNC controller. I always used Isolator
> Pro for toolpaths when I did mechanical etching.
> 
> I played around with "scratch and etch" too for a while. I also 
plotted directly to copper using modified drafting pens
> filled with acrylic floor polish. The smallest pen I have found 
locally is a .18 mm tip technical pen. That produces a trace
> of .0070866 wide. So it's a 7 mil trace. I successfully plotted and 
etched some 48 pin TSOP to 48 pin DIP adapter
> boards so I could read some flash roms on my programmer. But it was 
SLOW!  Also filled areas like pads
> had concentric circles in them where the carbide pen tip scratched 
into the just layed down path of resist.
> 
> However, using Inkjets produces solid fills with no voids. No 
special software is needed either. All you need is 
> something that can print your gerber files to a standard printer.
> 
> Modern inkjet printers are fast and are accurate enough to do some 
very small trace widths and spacings.
> 
> You could also lay down solder mask and the component identifiers 
using the same modified printer.
> 
> While I agree that the scratch and etch idea is great, and has some 
benefits over direct resist application, the biggest 
> downside I see is the problem of the toolpath generation for the 
average user.  Also, the tool must be tightly controlled
> to produce the necessary isolation path widths. For me the perfect 
width would be a 5 mil tool. But will a tool that is 
> .005 wide cut a clean swipe through the bluing without splintered 
edges?  If your tool has a very sharp tip, then you'll 
> need multiple passes to get a 5 to 10 mill isolation path. I never 
got a clean enough path through the resist. "furry" 
> or jagged edges on traces also cause lots of noise problems on high 
speed circuits.
> 
> The market for these products are not just hobbiests. There are a 
lot of us guys out there that make their living in the 
> electronics industry that would LOVE to have something to quickly 
make a board without having to send it out!
> Lots of corporations would buy them for the EE labs!
> 
> I just wish someone would run with it and work out all the bugs so 
I could just buy one. I want to make boards not
> tools to make boards.
> 
> later,
> Larry E.
> 
> 
> 
>   ----- Original Message ----- 
>   From: crankorgan 
>   To: Homebrew_PCBs@y... 
>   Sent: Saturday, September 14, 2002 6:41 AM
>   Subject: [Homebrew_PCBs] Re: Inkjet printing PC boards
> 
> 
>   Larry,
>         I sell plans for a PCBmill (Brute) and I just finished a 
>   machine that will mill or draw simple boards. (Morph)
>         Months ago I brought up the idea of Scratch and Etch. This
>   idea is not dead. First I developed a super simple CNC plotter. 
Now
>   I have a machine strong enough to drag a scribe through the 
blueing.
>   Several people tried Scratch and Etch With good results. Coating 
the 
>   whole board and then scribing and isolation between pads for 
etching 
>   seems easier.
> 
>                                              Crankorgan John 
> 
> 
>   --- In Homebrew_PCBs@y..., "Larry Edington" <ledington@a...> 
wrote:
>   > This is a copy of a reply I just posted in 
sci.electronics.design. 
>   I thought I would
>   > post it here as well for you folks to pursue if you are 
interested 
>   in it. Maybe
>   > Crankorgan John could go work up some plans for it. It's 
promising 
>   technology
>   > but I like working with boards more than belts and gears.
>   > 
>   > 
>   > > >Has anyone every tried putting Etch resist  Ink in a 
BubbleJet 
>   or InkJet
>   > > >printer and printing a PCB design directy onto the copper 
side 
>   of a PCB.
>   > 
>   > As a matter of fact I have. I thought about turning this into a 
>   commercial product, but
>   > I just don't have the time. Too many other projects to do. I 
even 
>   went so far as to 
>   > turn an inkjet into a flatbed plotter. The problem there is 
>   converting the stepper motor driven
>   > motion of the platten roller into linear motion with the 
stepper 
>   using belts or gears or
>   > electronic gear ratio reduction for the steps. All three 
methods 
>   work but I like the 
>   > belt and gears method best.
>   > 
>   > I tried modifying printers to feed a board through as is, but 
that 
>   was just too much trouble.
>   > Some would feed thin stock just fine but others wouldn't. The 
flat 
>   bed approach solves that.
>   > Plus the flat bed approach with some simple guide pins lets you 
do 
>   double sided boards with
>   > accurate side to side registration.
>   > 
>   > For ink, I found two things that work well standing up to the 
>   etchant.
>   > 
>   > Acrylic Floor Polish.  
>   > Shellac 
>   > 
>   > Floor polish ( sometimes called wax ) ( I used the Future 
brand ) 
>   works well and won't gum
>   > up the printheads as easily as Shellac does.
>   > 
>   > Floor polish is removed with Ammonia.
>   > 
>   > Shellac with Denatured Alcohol. 
>   > 
>   > I used three different types of printers. A Lexmark where the 
head 
>   is built into the cartridge,
>   > an HP where the printhead is separate from the cartridge but 
still 
>   uses thermal "bubble" jet
>   > technology and an Epson which uses piezoelectric technology.
>   > 
>   > The winner was the Lexmark. Easy cartridge to refill and cheap 
>   enough to replace.
>   > 
>   > The problem in all this is that to use straight "ink" that is 
very 
>   water ( and then etchant ) proof
>   > is, it will dry on your printhead orifices. The solution to 
that is 
>   a valve. One path to ink, one path
>   > to a flushing fluid. Before you print the board, run a cycle 
>   of "ink" to clear out all your flush fluid.
>   > Once you have finished printing, run a cycle of flushing fluid 
to 
>   purge all your "ink".
>   > 
>   > Ammonia diluted with water works great on the acrylic polish 
ink. 
>   You can even put a little regular
>   > inkjet ink into it to color it so it's easier to see on the PC 
>   board blank.
>   > 
>   > Once you get the "ink" on the board and have etched it, you can 
>   clean it off with just a quick spray of
>   > Windex or other ammonia based cleaner.
>   > 
>   > I have no idea as to the benefits or problems with acrylics as 
>   conformal coatings but I plan to try it 
>   > some day on a finished board. Just dip it in Future polish and 
see 
>   what happens!
>   > 
>   > Another thought I had was a PVA ( poly vinyl alcohol ) based 
ink 
>   but the PVA I had on hand didn't
>   > thin out well to run in an inkjet. The acrylic ink worked well 
>   enough so I didn't really pursue PVA much.
>   > 
>   > Now go have fun......
>   > 
>   > later,
>   > Larry Edington.
>   > 
>   > 
>   > [Non-text portions of this message have been removed]
> 
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