Homebrew PCBs

Wow Paul,
Your fingers must be ready for a vacation after all that.
Thanks, This will take me a little while to digest.
I am looking forward to trying it none the less. I have
been putting this Mach. toghther for a while. I did notice
on another cnc project, that my table is slighty off on the
Y axis, but I have a quick fix for that.
I believe I have Eagle soft ware all ready. It's on my Cnc
computer, so I will check.
Thanks again.
Mark

--- In Homebrew_PCBs@yahoogroups.com, Paul Ward <pward123@...> wrote:
>
> Oh boy, have you opened a can of worms.  I've yet to perform isolation
> routing, but have been doing quite a bit of research about it recently.
> 
> Design Software:
> It seems like Eagle PCB (http://www.cadsoftusa.com/) is a very popular
> application to design board layouts.  I've done some work with it, and I
> find it pretty easy to use.  You can generate your schematic and board
> layout with it.  The biggest problem I have with Eagle is finding the right
> component in the library.  Oh, the freebie hobby version is also limited to
> roughly 3"x4" boards.
> 
> Generating Gcode from Eagle:
> Once you've designed a layout, you'll need to generate gcode from the board.
> Eagle has a user expandable scripting feature called ULP.  I've seen quite a
> bit of discussion about a ULP script called pcb-gcode.  You can find it at
> the Eagle ULP download page
> (http://www.cadsoftusa.com/cgi-bin/download.pl?page=/home/cadsoft/html_publi
> c/download.htm.en&dir=eagle/userfiles/ulp).
> 
> From what I've read, the Gcode that pcb-gcode creates is not very well
> optimized.  There's another ULP on that same page that will supposedly
> optimize the generated gcode called pcb-gcode-wizard.
> 
> Drilling the Board and Vias:
> Some of the posts I've seen recommend drilling the board before performing
> isolation routing.  If you're using vias, you'll need to worry about plated
> through holes.  Some people use through-hole rivets
> (http://www.megauk.com/through_hole_rivets.php) but they could come loose
> over time and are not dirt cheap.  LPKF has a package
> (http://www.lpkf.com/products/rapid-pcb-prototyping/through-hole-plating/che
> mical-free/index.htm) that allows you to do through holes, but I think
> that's pretty pricey.  Some people just take a copper wire, stick it in the
> hole and fill it with solder.
> 
> Over at VoodooEngineering.com, they have a pretty good video demonstrating a
> DIY electroplating method to deal with vias.  You can find that at
> (http://www.voodooengineering.com/index.php/pcbprocess/plating).  Going this
> route will require generating a plating mask.  Even though they haven't
> posted videos for actual routing, there's a bunch of good video footage here
> that may be worth your time.
> 
> Fine Pitch SMD Problems:
> The biggest problem that you're likely to face if you want to do fine pitch
> SMD components is the epoxy layer between the fiberglass and the copper
> laminate is not uniform.  Even 1-2 mils of thickness variation can prevent
> you from successfully performing isolation of small SMD components.  So,
> even if you've milled your spoilboard complete flat relative to the spindle,
> the epoxy will vary enough on a single board to cause a ton of headaches.
> 
> Over in the PCB Milling forum on CNCZone, you'll find a thread
> (http://www.cnczone.com/forums/pcb_milling/82628-cheap_simple_height-probing
> .html) where people have been performing a probe pass to measure the
> thickness of the board in a grid pattern and then extrapolate the height for
> the tool path.  About half way through the thread is mention of a python
> script that will perform the probe pass and alter your gcode to reflect the
> results.
> 
> Another method of dealing with the variation is to use a floating head
> design for your Z axis.  The documentation for doing this is pretty sparse
> with most of the information I've found being related to plasma cutters.
> The best illustration of a floating dead design for a spindle is the January
> 5, 2006 pictures on this page (http://www.robio.be/cnc/final/index.htm) .
> 
> Solder Stencil:
> The millpcbs site has quite a bit of information that you may find useful.
> Here's one page 
> (http://www.millpcbs.com/index.php?option=com_content&view=article&id=28&Ite
> mid=49) specifically talking about how to create a solder stencil.
> 
> Solder Mask:
> Once you manage to perform all of the gyrations above, you'll still need to
> worry about a solder mask.  Although Retromaster doesn't use isolation
> routing, he has documented a method
> (http://retromaster.wordpress.com/pcb-making/) he uses for creating a solder
> mask that looks crazy good.
>  
> Hope this helps and Good Luck!
> Paul
>  
> 
> 
> 
> 
> [Non-text portions of this message have been removed]
>