Seems a lightbox is easier and cheaper than making a laminator...
Ballendo
--- In
Homebrew_PCBs@yahoogroups.com, Les Newell <lesnewell@h...>
wrote:
>
> There isn't much to my system. I use an Epson colour printer with
Rapid
> Electronics inkjet transparency. I found that green works best.
Black
> and red both seem to have a crazing effect which can cause broken
> tracks. This is with the new Durabrite inks. The older inks seemed
to
> work better but my old Stylus Color 600 died. The layout has to be
> printed so the ink side goes towards the board.
>
> The light box is a simple wooden box with four UV tubes about
100mm
> under sheet of glass. There is a sheet of aluminium foil under the
tubes
> to reflect the light upwards. There is a lid to clamp the board in
place
> while exposing it and I found that a couple of layers of bubble
wrap
> between the lid and board gives a good even pressure. When you
first set
> up you need to work out how long an exposure is needed. This is
pretty
> simple. Print a layout and stick the transparency to a piece of
board
> with sticky tape. On the back of the board make a series of marks,
> roughly even spaced. About 7 or 8 will probably do. Place it in
the
> light box with a piece of aluminium foil between the board and the
> glass, with one edge lined up with the first mark leaving a small
strip
> exposed. Expose the board for 1 minute, move the strip to line up
with
> the next mark, expose for 1 minute and so on. You now have a board
that
> at one end has been exposed for 8 or 9 minutes and the other end
that
> has only been exposed for 1 minute. When you develop the board it
is
> quite easy to see where it is under and over developed. Find the
best
> part of the board and you will know how long you need to expose
the
> board. This is a bit tedious but you only need to do it once. Some
> boards are very sensitive so you may have to repeat the experiment
using
> different timing.
>
> Exposure time varies as the tubes warm up so I usually turn them
on
> 10-15 minutes in advance to give them time to warm up. I use
precoated
> board and I can recommend Microtrak board from Mega Electronics -
I
> think It is actually made by Bungard. It has a thin coating which
> reduces undercutting and the resist coating is fairly tolerant to
> under/over exposure. Developer is a level teaspoon of caustic
soda
> granules in a litre of water. A few drops of detergent added to
the mix
> helps the developer wet the surface. I drop the board in a tray,
add
> enough developer to cover the surface then rock the tray. As
developing
> progresses you see streaks of darker resist appearing in the
developer.
> Once they stop appearing the board is done. A quick dip in the
etch tank
> will hilight any areas that have been missed.
>
> I normally use .012" track+gap (~0.3mm) because I know it is
reliable.
> 0.25T&G shouldn't be a problem. The most important thing is to get
a
> good quality print out of your printer. I tried a Lexmark and that
> produced a very fuzzy print.
>
> Les
>
> about 100mm awa
>
> Jim Miller wrote:
>
> >Hi Les
> >
> >Is your method written up somewhere?
> >
> >What sort of linewidths do you have success with? I'm looking at
doing some
> >work with AD9958 this winter and it has 0.25mm pads on 0.5mm
pitch.
> >
> >tnx
> >jim
> >
> >
> >
> >
> >
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