Homebrew PCBs

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 
> >
> >
> >
> >
> >
> >
> >Be sure to visit the group home and check for new Links, Files, 
and Photos:
> >http://groups.yahoo.com/group/Homebrew_PCBs
> >
> >If Files or Photos are running short of space, post them here:
> >http://groups.yahoo.com/group/Homebrew_PCBs_Archives/ 
> >Yahoo! Groups Links
> >
> >
> >
> > 
> >
> >
> >
> >  
> >
>