Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

I think the thing that would ease alignment of vias isn't just via size, but via landing size.

David Bobb -- N5MUX

On Aug 16, 2014 10:12 AM, "Mark Lerman mlerman@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> wrote:

 

A little out of my league <smile>. My needs are simpler, though I
often do use TQFP packages. Those, however, often need vias under the
chip, which I can't do. To make alignment less critical I would use
larger vias so you can't "miss" as easily.

Mark

At 09:38 AM 8/16/2014, you wrote:
>On Sat, 16 Aug 2014 08:51:49 -0400, you wrote:
>
> >Thanks, Harvey, for the detailed description - Very interesting
> >setup. One of these days I'll work on something similar, though I
> >rarely drill a lot of holes. I use almost exclusively smt and usually
> >make single sided pcbs using zero ohm resistors as jumpers.
> >
>
>I do double sided boards, with the boards made from two .021 boards
>epoxied together (use 1 hour epoxy!). Alignment is very critical and
>the drilling setup (finally!) makes that work a lot better. Since I'm
>doing 64/100/144 pin TQFP chips, I can't live with the luxury of
>exclusively resistive jumpers.
>
>Latest project involves a graphics panel driver with an S1D13781
>graphics chip (Epson, anyone wanting to use it please talk to me,
>there are some non-obvious things you need to do to make it work). an
>Xmega, a touch panel controller, -24 volt supply, I2C communications
>(dual channel).
>
>Harvey
>
> >Mark
> >
> >
> >At 06:50 PM 8/15/2014, you wrote:
> >>On Fri, 15 Aug 2014 12:52:18 -0400, you wrote:
> >>
> >> >Hello Harvey,
> >> >
> >> >I'm interested in getting more information on your drilling setup,
> >> >mostly the optical stuff - camera, software, monitor. What supplies
> >> >the reticule image for the crosshairs?
> >>
> >>OK, in short. The optical stuff is a 12 volt/24vac camera with almost
> >>any lens that works well. You want to move it out away from the CCD
> >>so that you have the equivalent of a closeup extender.
> >>
> >>That goes to a standard color monitor. This is an LCD monitor that I
> >>found (runs off 12 volts DC), and has an overlay with a graticule on
> >>it. I've been tempted to make it more complicated by adding a
> >>crosshair generator, but that'd be another PC board and some video
> >>work. The graticule is easier. Just make the pattern on a
> >>transparency and put it over the monitor itself. Almost any old TV
> >>would work.
> >>
> >>The software is custom, and is a simple Z axis setup. There are two
> >>pushbuttons (green/red) and a rotary encoder with a push switch
> >>(Electronics goldmine sold them). There's an end travel (and top
> >>travel) led sensor.
> >>
> >>Boot up, the display says to push green to home. That homes the drill
> >>and runs it up to the rest position. pushing the footswitch (or the
> >>green pushbutton) starts a drill cycle, three speeds possible, up to
> >>the drill top position. At that point the drill retreats back to the
> >>rest position and turns off the Proxxon tool (solid state relay, works
> >>better with the 12 volt model and transformer).
> >>
> >>Pushing the red button puts the drill at the top position, which is
> >>where I can change the bit from the top.
> >>
> >>Pushing in the rotary switch/encoder put it into an adjust mode, where
> >>I can set the rest and top positions (stored in the processor's
> >>eprom).
> >>
> >>Basically, the software is not all that complicated, but does rely on
> >>an infrastructure of display drivers (it's a smart display that I
> >>built), a modified keyboard driver package, and a few other bits and
> >>pieces.
> >>
> >>Physically, the camera is mounted on a PACE hot air station stand (I
> >>managed to find two for not so much money), which gives me an
> >>overarching arm for the camera. I can move it up and down to focus
> >>the camera and move it out of the way for drill change. I suppose
> >>another enhancement would be to put a stepper drive on that.
> >>
> >>You will have to align the camera center point to the tip of the
> >>drill. In my case, the adjustment is entirely mechanical, with the
> >>camera swinging left/right on the mounting screw, but tilted (spring
> >>used on screw) forwards/backwards as needed. That's a trifle awkward,
> >>and the electronic crosshair generator would be better. That would
> >>require a small CPLD, a sync separator, a synchronized pixel clock,
> >>and some counters. Ideally, the graticule has ticks on both axis
> >>lines, since that helps align the center of large holes.
> >>
> >>The smallest hole I drill is 0.021 for a via, and I estimate that I
> >>can repeat that hole to within 0.002 inches roughly. The size of that
> >>hole on the monitor is the critical part.
> >>
> >>You'll want to backlight the board. Red light may be most useful, but
> >>I haven't experimented with that yet.
> >>
> >>Hope that this helps.
> >>
> >>Harvey
> >>
> >>
> >> >
> >> >Thanks.
> >> >
> >> >Mark
> >>
> >>
> >>
> >>------------------------------------
> >>Posted by: Harvey White <madyn@...>
> >>------------------------------------
> >>
> >>Be sure to visit the group home and check for new Links, Files, and Photos:
> >>http://groups.yahoo.com/group/Homebrew_PCBs
> >>------------------------------------
> >>
> >>Yahoo Groups Links
> >>
> >>
> >>
>
>
>
>------------------------------------
>Posted by: Harvey White <madyn@...>
>------------------------------------
>
>Be sure to visit the group home and check for new Links, Files, and Photos:
>http://groups.yahoo.com/group/Homebrew_PCBs
>------------------------------------
>
>Yahoo Groups Links
>
>
>