Hi Hans,
Milling circuit boards is actually called Mechanical Etching.
I call it milling because that's what it actually is. When I post
sites to look at. They have software that is first for making PCBoards
but they also have milling as a second step.
The milling cost for a single sided board 4 x 6". The board is
$2 the bit is $8 and the drill bit is $.79. So even with shipping I
can make a board for under $12. Your method has to be way cheaper.
Up until now I am still doing the holes on a Dremel drill press. I
could let the mill do it!
The advantage to milling is you can walk away during the
milling process. Every board is useable. The most important part is if
you use GCode to run the machine you overlap into CNC. This along
with using TurboCad for the DXF files teaches you drafting. I have
be drafting for years. Comes in handy! The hobby gets more interesting
while staying very cheap! That's if you build your own stuff!
John
--- In Homebrew_PCBs@y..., hans@c... wrote:
> John,
> OK just wanted to know.
> Time is important, it's the main reason I don't have a board shop
make
> two side prototypes unless they are very densely packed.
> I have a reasonable setup and now expose both sides at once, which
cuts
> down on development and etching.
> I timed a session for a small board, that needed about 120 holes,
from
> the time I print transparencies on my laserjet until it's drilled
> which also includes silver plating both side, about 1 hour.
> The most time consuming issue is still via connections. I use
eyelet's
> and Mill-Max pins as well as Harwin via pins. For most DIP I
use "high"
> machined sockets and solder top and bottom, for really tight via's I
> drill 16 mil and rivet stretched 22 swg wire in place, until
recently
> that was my standard way to do via's.
> Many people I know tend to throw away the ferric chloride and lye
> developer far to soon. My ferric chloride is over 5-7 years old and
> still completes etching in 9-11 minute (temperature influences the
time)
> Lye developer is cheap and can be purchased at the grocery store I
mix
> it and once I have a good solution I use it for months.
> All Transparencies material for laser jets are not equal, and I have
> tried every on I could buy in small packets.
> The best for my HP LJ1100 at 600 dpi is Apollo CG7060 it will do 5
mill
> every day. Then next is 3M CG3300 which is good for 8-10 mil. What I
> found with many others is they tend to have bare spots on smaller
> traces.
> I do not work in darkrooms, there is far too much hype about how
> sensitive the pre-sensitized material is, I work in a north facing
rom
> and close the venetian blinds and have a 120 Watt bulb as light
source
> for room lighting. I use Datek material.
> Exposure bulbs are GE 500W EBW 282 which has the wording average
life 6
> hours on it.... I have been using them for years... ! They get VERY
hot
> and the bulb holder should be ceramic.
> For exposure of the board I align the transparencies and staple them
> together, then slip the PCB between them, then sandwich the lot
between
> two sheets of 8"X10" glass (Home Depot) clamped together using four
> small Binder Clips, and position the sandwich between the two bulbs
at
> distance 6 inches from bulb to glass. I expose for 110 seconds for
new
> board, and if I know some older bits ( I save all small bits) are
older
> I may increase the time to 120-130 seconds.
> Actual development time in Lye is about 60-90 seconds. Wear thin
rubber
> gloves or the lye will eat at your skin, and do NOT get lye in your
eyes
> it will blind you. If contact is made between lye and skin flush
with
> LOTS of water.
> Once developed, I dry off with a paper towel, there is another
myth, the
> green coating is not as delicate as many people hype on about....
It is
> more brittle and of course can be scratched, but it can be swiped
dry
> and handle directly.
> Once dry, I inspect and make sure the development went OK, if not I
> simply put it back in the Lye and continue, what I'm looking for it
a
> super thin layer of the green coating that may still be on some
area's,
> and this indicates more development is needed. I touch up anything
I
> need to using a Laundry marker pen, the kind that people pay $$$ for
> that are called etch resistant ! Marks-A-Lot works fine for large
areas
> and Sharpie markers #13601 for mid width and Sharpie #37000 for
fine
> work.
> I drill using carbide drills and a Dremel in a drill press stand...
> Silver plating I use Cool-Amp powder, it's expensive but far easier
to
> use than the Tin-It crap... Cool-Amp costs about $40 for 4 oz.
however I
> have been using it for a long long time and have over half left... I
> reuse the same rag pad and sometimes simply wet the pad and use the
> residual from the last session.
>
> For production, board shop is the only answer... 4pcb.com are still
> doing two prototype boards for $35 each upto 64 sq. ins. not other
cost
> involved, but they have a 5-10 days wait.... That's why I still
make my
> own board when I can.
>
> I called the CA outfit (the link you posted a few days back) and
talked
> with the owner that makes the PCB milling system, I think he has a
good
> product, but it's out of my price range...
>
> I can't see me milling boards, if you only get about 600 inches per
bit,
> and the reduced resolution simply limits it usefulness.
>
> Anyway that's how I do my boards, just wish I could fine a very
simple
> through hole plating system.
>
> Hans W
> PS here is a picture of a silver plated PCB I made some time ago...
> http://hans-w.com/9909-01A_1.jpg
>
>
>
>
>
>
> crankorgan wrote:
>
> > Hi Hans,
> > I have no problem with etching. I will even say that Proto
> > board then Perf onto etched PCBoard. Right now the boards I sell
> > are milled. If sales get higher I will have a run of boards
> > etched. I don't like the acid method because I have had some
> > accidents in the past. I feel all methods of making circuit
> > boards should be discussed. Going from schematic to PCBoard
> > has several routes also.
> >
> > John
> >
> >
> >
> > --- In Homebrew_PCBs@y..., hans@c... wrote:
> > > Been following all this about perf. boards and milling etc.
> > >
> > > I like the idea of milling but it seems the prep. work is
> > tremendous.
> > >
> > > Doing pref. boards then PCB seems like hard labor.
> > >
> > > I'd like to have comments as to why pre-sensitzed PCB and
etching
> > is not
> > > mentioned and what you consider is so bad with it ?
> > >
> > > Best Regards
> > > Hans W
> >
> >
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